BQ27541DRZR - Texas Instruments

Battery Pack

PACK–

PROTECTION

PACK+

SCL

bq27541

LDO REG25

REGIN

Vcc

SRP

SRN

BAT

Vss

HDQ

SDA

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

Single Cell Li-Ion Battery Fuel Gauge for Battery Pack Integration

Check for Samples: bq27541

1FEATURES APPLICATIONS

• Smartphones

23• Battery Fuel Gauge for 1-Series Li-Ion

Applications • PDAs

• Digital Still and Video Cameras

• Microcontroller Peripheral Provides: • Handheld Terminals

– Accurate Battery Fuel Gauging • MP3 or Multimedia Players

– Internal Temperature Sensor for System

Temperature Reporting DESCRIPTION

– SHA-1/HMAC Authentication The Texas Instruments bq27541 Li-Ion battery fuel

– 96 Bytes of Non-Volatile Scratch Pad gauge is a microcontroller peripheral that provides

FLASH fuel gauging for single-cell Li-Ion battery packs. The

• Battery Fuel Gauging Based on Patented device requires little system microcontroller firmware

Impedance Track™ Technology development for accurate battery fuel gauging. The

bq27541 resides within the battery pack or on the

– Models Battery Discharge Curve for system’s main-board with an embedded battery

Accurate Time-To-Empty Predictions (nonremovable).

– Automatically Adjusts for Battery Aging,

Battery Self-Discharge, and The bq27541 uses the patented Impedance Track™

algorithm for fuel gauging, and provides information

Temperature/Rate Inefficiencies such as remaining battery capacity (mAh),

– Low-Value Sense Resistor (5 mΩto 20 mΩ)state-of-charge (%), run-time to empty (min.), battery

• HDQ and I2C™ Interface Formats for voltage (mV), and temperature (°C).

Communication with Host System The bq27541 also features integrated support for

• Small 12-pin 2,5 mm × 4 mm SON Package secure battery pack authentication, using the

SHA-1/HMAC authentication algorithm.

TYPICAL APPLICATION

1Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas

Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

2Impedance Track is a trademark of Texas Instruments.

3I2C is a trademark of Phillips Corporation.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

REGIN

BAT

Vcc

Vss

SE 12

SRN

SRP

REG25 SCL

SDA

HDQ

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with

appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.

ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more

susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.

DEVICE INFORMATION

AVAILABLE OPTIONS

PART NUMBER PACKAGE TA COMMUNICATION TAPE and REEL

FORMAT QUANTITY

bq27541DRZR 3000

12-pin, 2,5-mm × 4-mm SON –40°C to 85°C I2C, HDQ(1)

bq27541DRZT 250

(1) bq27541 is shipped in I2C mode

bq27541

(TOP VIEW)

TERMINAL FUNCTIONS

TERMINAL DESCRIPTION

NAME NO. TYPE(1)

BAT 4 I Cell-voltage measurement input. ADC input. Decouple with 0.1mF capacitor.

REG25 2 P 2.5V output voltage of the internal integrated LDO. Connect a minimum 0.47mF ceramic capacitor.

REGIN 3 P The input voltage for the internal integrated LDO. Connect a 0.1mF ceramic capacitor.

SCL 11 I Slave I2C serial communications clock input line for communication with system (Slave). Use with 10 kΩ

pull-up resistor (typical).

SDA 10 I/O Slave I2C serial communications data line for communication with system (Slave). Open-drain I/O. Use

with 10 kΩpull-up resistor (typical).

SE 1 O Shutdown Enable output. Open-drain.

HDQ 12 I/O HDQ serial communications line (Slave). Open-drain.

SRN 8 IA Analog input pin connected to the internal coulomb counter where SRN is nearest the PACK- connection.

Connect to 5-mΩto 20-mΩsense resistor.

SRP 7 IA Analog input pin connected to the internal coulomb counter where SRP is nearest the CELL- connection.

Connect to 5-mΩto 20-mΩsense resistor

TS 9 IA Pack thermistor voltage sense (use 103AT-type thermistor). ADC input

Vcc 5 P Processor power input. The minimum 0.47mF capacitor connected to REG25 should be close to Vcc.

Vss 6 P Device ground

(1) I/O = Digital input/output, IA = Analog input, P = Power connection

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

ELECTRICAL SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

over operating free-air temperature range (unless otherwise noted)(1)

VALUE UNIT

VIRegulator input, REGIN –0.3 to 24 V

VCC Supply voltage range –0.3 to 2.75 V

VIOD Open-drain I/O pins (SDA, SCL, HDQ) –0.3 to 6 V

VBAT BAT input, (pin 4) –0.3 to 6 V

VIInput voltage range to all others (pins 1, 7, 8, 9) –0.3 to VCC + 0.3 V

Human Body Model (HBM), BAT pin 1.5

ESD kV

Human Body Model (HBM), all pins 2

TFFunctional temperature range –40 to 100 °C

Tstg Storage temperature range –65 to 150 °C

(1) Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. These are stress ratings

only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating

conditions is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

DISSIPATION RATINGS TA≤40°C DERATING FACTOR

PACKAGE(1) RqJA

POWER RATING TA≤40°C

12-pin DRZ(2) 482 mW 5.67 mW/°C 176°C/W

(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI

website at www.ti.com.

(2) This data is based on using a 4-layer JEDEC high-K board with the exposed die pad connected to a Cu pad on the board. The board

pad is connected to the ground plane by a 2- × 2-via matrix.

RECOMMENDED OPERATING CONDITIONS

TA= -40°C to 85°C; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V (unless otherwise noted)

PARAMETER Test CONDITION MIN TYP MAX UNIT

No operating restrictions 2.7 5.5

VISupply voltage, REGIN V

No FLASH writes 2.45 2.7

Fuel gauge in NORMAL mode. ILOAD >

ICC Normal operating mode current (1) 131 mA

Sleep Current

Fuel gauge in SLEEP mode.

I(SLP) Low-power operating mode current (1) 60 mA

ILOAD <Sleep Current

Fuel gauge in FULLSLEEP mode.

I(FULLSLP) Low-power operating mode current (1) 21 mA

ILOAD <Sleep Current

Fuel gauge in HIBERNATE mode.

I(HIB) Hibernate operating mode current (1) 6mA

ILOAD <Hibernate Current

Output voltage low (HDQ, SDA, SCL,

VOL IOL = 3 mA 0.4 V

SE)

VOH(PP) Output high voltage (SE) IOH = -1 mA VCC–0.5 V

VOH(OD) Output high voltage (HDQ, SDA, SCL) External pull-up resistor connected to Vcc VCC–0.5 V

VIL Input voltage low (HDQ, SDA, SCL) –0.3 0.6 V

VIH Input voltage high (HDQ, SDA, SCL) 1.2 6 V

V(A1) Input voltage range (TS) VSS–0.125 2 V

V(A2) Input voltage range (BAT) VSS–0.125 5 V

V(A3) Input voltage range (SRP, SRN) VSS–0.125 0.125 V

Ilkg Input leakage current (I/O pins) 0.3 mA

tPUCD Power-up communication delay 250 ms

(1) Specified by design. Not tested in production.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

POWER-ON RESET

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VIT+ Positive-going battery voltage input at VCC 2.05 2.20 2.31 V

VHYS Power-on reset hysteresis 45 115 185 mV

2.5 V LDO REGULATOR(1)

TA= –40°C to 85°C, C(REG) = 0.47 mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITION MIN NOM MAX UNIT

2.7 V ≤V(REGIN) ≤5.5 V, TA= –40°C to 85°C 2.42 2.48 2.57 V

IOUT ≤16mA

Regulator output voltage,

VOREG25 2.45 V ≤V(REGIN) < 2.7 V (low TA= –40°C to 85°C 2.4 V

battery), IOUT ≤3mA

2.7 V, IOUT ≤16 mA 280

VDO Regulator dropout voltage TA= –40°C to 85°C mV

2.45 V, IOUT ≤3 mA 50

V(REGIN) = 3.6 V,

Regulator output change

ΔV(REGTEMP) TA= –40°C to 85°C 0.3%

with temperature IOUT = 16 mA

ΔV(REGLINE) Line regulation 2.7 V ≤V(REGIN) ≤5.5 V, IOUT = 16 mA 11 25 mV

0.2 mA ≤IOUT ≤3 mA, V(REGIN) = 2.45 V 34 40

ΔV(REGLOAD) Load regulation mV

3 mA ≤IOUT ≤16 mA, V(REGIN) = 2.7 V 31

IOS (2) Short circuit current limit V(REG25) = 0 V, TA= –40°C to 85°C 250 mA

(1) LDO output current, IOUT, is the sum of internal and external load currents.

(2) Specified by design. Not production tested.

INTERNAL TEMPERATURE SENSOR CHARACTERISTICS

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

G(TEMP) Temperature sensor voltage gain –2 mV/°C

HIGH FREQUENCY OSCILLATOR

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

fOSC Operating frequency 2.097 MHz

TA= 0°C to 60°C –2.0% 0.38% 2.0%

fEIO Frequency error(1) (2) TA= –20°C to 70°C –3.0% 0.38% 3.0%

TA= –40°C to 85°C -4.5% 0.38% 4.5%

tSXO Start-up time(3) 2.5 5 ms

(1) The frequency error is measured from 2.097 MHz.

(2) The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA= 25°C.

(3) The startup time is defined as the time it takes for the oscillator output frequency to be ±3% of typical oscillator frequency.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

LOW FREQUENCY OSCILLATOR

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

fOSC Operating frequency 32.768 KHz

TA= 0°C to 60°C –1.5% 0.25% 1.5%

fEIO Frequency error(1) (2) TA= –20°C to 70°C –2.5% 0.25% 2.5%

TA= –40°C to 85°C -4.0% 0.25% 4.0%

tSXO Start-up time(3) 500 ms

(1) The frequency drift is included and measured from the trimmed frequency at VCC = 2.5 V, TA= 25°C.

(2) The frequency error is measured from 32.768 KHz.

(3) The startup time is defined as the time it takes for the oscillator output frequency to be ±3% of typical oscillator frequency.

INTEGRATING ADC (COULOMB COUNTER) CHARACTERISTICS

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VIN(SR) Input voltage range, V(SRN) and V(SRP) VSR = V(SRN) – V(SRP) –0.125 0.125 V

tCONV(SR) Conversion time Single conversion 1 s

Resolution 14 15 bits

VOS(SR) Input offset 10 mV

INL Integral nonlinearity error ±0.007 ±0.034 FSR

ZIN(SR) Effective input resistance(1) 2.5 MΩ

Ilkg(SR) Input leakage current(1) 0.3 mA

(1) Specified by design. Not production tested.

ADC (TEMPERATURE AND CELL MEASUREMENT) CHARACTERISTICS

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VIN(ADC) Input voltage range –0.2 1 V

tCONV(ADC) Conversion time 125 ms

Resolution 14 15 bits

VOS(ADC) Input offset 1 mV

Z(ADC1) Effective input resistance (TS) (1) 8 MΩ

Z(ADC2) Effective input resistance (BAT)(1) bq27541 not measuring cell voltage 8 MΩ

bq27541 measuring cell voltage 100 kΩ

Ilkg(ADC) Input leakage current(1) 0.3 mA

(1) Specified by design. Not production tested.

DATA FLASH MEMORY CHARACTERISTICS

TA= –40°C to 85°C, C(REG) = 0.47mF, 2.45 V < V(REGIN) = VBAT < 5.5 V; typical values at TA= 25°C and V(REGIN) = VBAT = 3.6 V

(unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

tDR Data retention(1) 10 Years

Flash programming write-cycles (1) 20,000 Cycles

tWORDPROG Word programming time(1) 2 ms

ICCPROG Flash-write supply current(1) 5 10 mA

(1) Specified by design. Not production tested.

Product Folder Link(s): bq27541

t(B) t(BR)

(a)BreakandBreakRecovery

(b)HostTransmittedBit

t(HW1)

t(HW0)

t(CYCD)

Break 7-Bit Address 1-Bit

R/W 8-BitData

t(RSPS)

(c)GaugeTransmitBit

t(DW1)

t(DW0)

(d)GaugetoHostResponse

t(CYCH)

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

HDQ COMMUNICATION TIMING CHARACTERISTICS

TA= –40°C to 85°C, CREG = 0.47mF, 2.45 V < VREGIN = VBAT < 5.5 V; typical values at TA= 25°C and VREGIN = VBAT = 3.6 V

(unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

t(CYCH) Cycle time, host to bq27541 190 ms

t(CYCD) Cycle time, bq27541 to host 190 205 250 ms

t(HW1) Host sends 1 to bq27541 0.5 50 ms

t(DW1) bq27541 sends 1 to host 32 50 ms

t(HW0) Host sends 0 to bq27541 86 145 ms

t(DW0) bq27541 sends 0 to host 80 145 ms

t(RSPS) Response time, bq27541 to host 190 320 ms

t(B) Break time 190 ms

t(BR) Break recovery time 40 ms

Figure 1. Timing Diagrams for HDQ Breaking (a), HDQ Host to bq27541 communication (b), bq27541 to

Host communication (c), and bq27541 to Host response format (d).

Product Folder Link(s): bq27541

tSU(STA)

SCL

SDA

tw(H) tw(L) tftrt(BUF)

td(STA)

REPEATED

START

th(DAT) tsu(DAT)

tftsu(STOP)

STOP START

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

I2C-COMPATIBLE INTERFACE COMMUNICATION TIMING CHARACTERISTICS

TA= –40°C to 85°C, CREG = 0.47mF, 2.45 V < VREGIN = VBAT < 5.5 V; typical values at TA= 25°C and VREGIN = VBAT = 3.6 V

(unless otherwise noted) PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

trSCL/SDA rise time 300 ns

tfSCL/SDA fall time 300 ns

tw(H) SCL pulse width (high) 600 ns

tw(L) SCL pulse width (low) 1.3 ms

tsu(STA) Setup for repeated start 600 ns

td(STA) Start to first falling edge of SCL 600 ns

tsu(DAT) Data setup time 1000 ns

th(DAT) Data hold time 0 ns

tsu(STOP) Setup time for stop 600 ns

tBUF Bus free time between stop and start 1.3 ms

fSCL Clock frequency 400 kHz

Figure 2. I2C-Compatible Interface Timing Diagrams

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

GENERAL DESCRIPTION

The bq27541 accurately predicts the battery capacity and other operational characteristics of a single Li-based

rechargeable cell. It can be interrogated by a system processor to provide cell information, such as

state-of-charge (SOC), time-to-empty (TTE) and time-to-full (TTF).

Information is accessed through a series of commands, called Standard Commands. Further capabilities are

provided by the additional Extended Commands set. Both sets of commands, indicated by the general format

Command( ), are used to read and write information contained within the bq27541 control and status registers,

as well as its data flash locations. Commands are sent from system to gauge using the bq27541’s serial

communications engine, and can be executed during application development, pack manufacture, or

end-equipment operation.

Cell information is stored in the bq27541 in non-volatile flash memory. Many of these data flash locations are

accessible during application development. They cannot, generally, be accessed directly during end-equipment

operation. Access to these locations is achieved by either use of the bq27541’s companion evaluation software,

through individual commands, or through a sequence of data-flash-access commands. To access a desired data

flash location, the correct data flash subclass and offset must be known.

The bq27541 provides 96 bytes of user-programmable data flash memory, partitioned into 3 32-byte blocks:

Manufacturer Info Block A, Manufacturer Info Block B, and Manufacturer Info Block C. This data space is

accessed through a data flash interface. For specifics on accessing the data flash, see section Manufacturer

Information Blocks. The key to the bq27541’s high-accuracy gas gauging prediction is Texas Instrument’s

proprietary Impedance Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties

to create state-of-charge predictions that can achieve less than 1% error across a wide variety of operating

conditions and over the lifetime of the battery.

The bq27541 measures charge/discharge activity by monitoring the voltage across a small-value series sense

resistor (5 mΩto 20 mΩtyp.) located between the CELL- and the battery’s PACK- terminal. When a cell is

attached to the bq27541, cell impedance is computed, based on cell current, cell open-circuit voltage (OCV), and

cell voltage under loading conditions.

The bq27501 external temperature sensing is optimized with the use of a high accuracy negative temperature

coefficient (NTC) thermistor with R25 = 10KΩ± 1% and B25/85 = 3435KΩ± 1% (such as Semitec 103AT for

measurement). The bq27501 can also be configured to use its internal temperature sensor. The bq27541 uses

temperature to monitor the battery-pack environment, which is used for fuel gauging and cell protection

functionality.

To minimize power consumption, the bq27541 has different power modes: NORMAL, SLEEP, FULLSLEEP,

HIBERNATE, and PRESHUTDOWN. The bq27541 passes automatically between these modes, depending upon

the occurrence of specific events, though a system processor can initiate some of these modes directly. More

details can be found in section Power Modes.

NOTE

FORMATTING CONVENTIONS IN THIS DOCUMENT:

Commands: italics with parentheses( ) and no breaking spaces. e.g. RemainingCapacity( )

Data Flash: italics,bold, and breaking spaces. e.g. Design Capacity

Data flash bits: italics,bold, and brackets[]. e.g: [LED1]

Modes and states: ALL CAPITALS. e.g. UNSEALED mode

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

STANDARD DATA COMMANDS

The bq27541 uses a series of 2-byte standard commands to enable system reading and writing of battery

information. Each standard command has an associated command-code pair, as indicated in Table 1. Because

each command consists of two bytes of data, two consecutive I2C transmissions must be executed both to

initiate the command function, and to read or write the corresponding two bytes of data. Additional options for

transferring data, such as spooling, are described in Section I2C Interface. Standard commands are accessible

in NORMAL operation.

Table 1. Standard Commands

NAME COMMAND CODE UNITS SEALED

ACCESS

Control( ) CNTL 0x00 / 0x01 N/A R/W

AtRate( ) AR 0x02 / 0x03 mA R/W

AtRateTimeToEmpty( ) ARTTE 0x04 / 0x05 Minutes R

Temperature( ) TEMP 0x06 / 0x07 0.1K R

Voltage( ) VOLT 0x08 / 0x09 mV R

Flags( ) FLAGS 0x0a / 0x0b N/A R

NominalAvailableCapacity( ) NAC 0x0c / 0x0d mAh R

FullAvailableCapacity( ) FAC 0x0e / 0x0f mAh R

RemainingCapacity( ) RM 0x10 / 0x11 mAh R

FullChargeCapacity( ) FCC 0x12 / 0x13 mAh R

AverageCurrent( ) AI 0x14 / 0x15 mA R

TimeToEmpty( ) TTE 0x16 / 0x17 Minutes R

TimeToFull( ) TTF 0x18 / 0x19 Minutes R

StandbyCurrent( ) SI 0x1a / 0x1b mA R

StandbyTimeToEmpty( ) STTE 0x1c / 0x1d Minutes R

MaxLoadCurrent( ) MLI 0x1e / 0x1f mA R

MaxLoadTimeToEmpty( ) MLTTE 0x20 / 0x21 Minutes R

AvailableEnergy( ) AE 0x22 / 0x23 10 mWhr R

AveragePower( ) AP 0x24 / 0x25 10 mW R

TTEatConstantPower( ) TTECP 0x26 / 0x27 Minutes R

Reserved RSVD 0x28 / 0x29 N/A R

CycleCount( ) CC 0x2a / 0x2b Counts R

StateOfCharge( ) SOC 0x2c / 0x2d % R

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

Control( ): 0x00/0x01

Issuing a Control( ) command requires a subsequent 2-byte subcommand. These additional bytes specify the

particular control function desired. The Control( ) command allows the system to control specific features of the

bq27541 during normal operation and additional features when the bq27541 is in different access modes, as

described in Table 2.

Table 2. Control( ) Subcommands

CNTL FUNCTION CNTL DATA SEALED DESCRIPTION

ACCESS

CONTROL_STATUS 0x0000 Yes Reports the status of DF Checksum, Hibernate, IT, etc.

DEVICE_TYPE 0x0001 Yes Reports the device type of 0x0541 (indicating bq27541)

FW_VERSION 0x0002 Yes Reports the firmware version on the device type

HW_VERSION 0x0003 Yes Reports the hardware version of the device type

DF_CHECKSUM 0x0004 No Enables a data flash checksum to be generated and reports on a read

RESET_DATA 0x0005 No Returns reset data

Reserved 0x0006 No Not to be used

PREV_MACWRITE 0x0007 No Returns previous MAC command code

CHEM_ID 0x0008 Yes Reports the chemical identifier of the Impedance Track™ configuration

SET_FULLSLEEP 0x0010 Yes Set the [FullSleep] bit in Control Status register to 1

SET_HIBERNATE 0x0011 Yes Forces CONTROL_STATUS [HIBERNATE] to 1

CLEAR_HIBERNATE 0x0012 Yes Forces CONTROL_STATUS [HIBERNATE] to 0

SET_SHUTDOWN 0x0013 Yes Enables the SE pin to change state

CLEAR_SHUTDOWN 0x0014 Yes Disables the SE pin from changing state

SEALED 0x0020 No Places the bq27541 is SEALED access mode

IT_ENABLE 0x0021 No Enables the Impedance Track™ algorithm

CAL_MODE 0x0040 No Places the bq27541 in calibration mode

RESET 0x0041 No Forces a full reset of the bq27541

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

CONTROL_STATUS: 0X0000

Instructs the fuel gauge to return status information to Control addresses 0x00/0x01. The status word includes

the following information.

Table 3. CONTROL_STATUS Bit Definitions

bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0

High Byte SE FAS SS CSV CCA BCA – –

Low Byte SHUTDOWN HIBERNATE FULLSLEEP SLEEP LDMD RUP_DIS VOK QEN

SE = Status bit indicating the SE pin is active. True when set (i.e. SE pin is low) . Default is 0.

FAS = Status bit indicating the bq27541 is in FULL ACCESS SEALED state. Active when set.

SS = Status bit indicating the bq27541 is in the SEALED State. Active when set.

CSV = Status bit indicating a valid data flash checksum has been generated. Active when set.

CCA = Status bit indicating the bq27541 Coulomb Counter Calibration routine is active. Active when set.

BCA = Status bit indicating the bq27541 Board Calibration routine is active. Active when set.

SHUTDOWN = Control bit indicating the fuel gauge can force its SE pin low to signal an external shutdown. True when set.

Default is 0.

HIBERNATE = Status bit indicating a request for entry into HIBERNATE from SLEEP mode has been issued. True when set. Default is

Control bit when set will put the bq27541 into the lower power state of SLEEP mode. It is not possible to monitor this bit

FULLSLEEP = because any communication will automatically clear it. The state can be detected by monitoring the power used by the

bq27541.

SLEEP = Status bit indicating the bq27541 is in SLEEP mode. True when set

LDMD = Status bit indicating the bq27541 Impedance Track™ algorithm using constant-power mode. True when set. Default is 0

(constant-current mode).

RUP_DIS = Status bit indicating the bq27541 Ra table updates are disabled. True when set.

VOK = Status bit indicating cell voltages are OK for Qmax updates. True when set.

QEN = Status bit indicating the bq27541 Qmax updates are enabled. True when set.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

DEVICE_TYPE: 0X0001

Instructs the fuel gauge to return the device type to addresses 0x00/0x01.

FW_VERSION: 0X0002

Instructs the fuel gauge to return the firmware version to addresses 0x00/0x01.

HW_VERSION: 0X0003

Instructs the fuel gauge to return the hardware version to addresses 0x00/0x01.

DF_CHECKSUM: 0X0004

Instructs the fuel gauge to compute the checksum of the data flash memory. The checksum value is written and

returned to addresses 0x00/0x01 (UNSEALED mode only). The checksum will not be calculated in SEALED

mode; however, the checksum value can still be read.

RESET_DATA: 0X0005

Instructs the fuel gauge to return the reset data to addresses 0x00/0x01, with the low byte (0x00) being the

number of full resets and the high byte (0x01) the number of partial resets.

PREV_MACWRITE: 0X0007

Instructs the fuel gauge to return the previous command written to addresses 0x00/0x01.

CHEM_ID: 0X0008

Instructs the fuel gauge to return the chemical identifier for the Impedance Track™ configuration to addresses

0x00/0x01.

SET_FULLSLEEP: 0X0010

Instructs the gas gauge to set the FullSleep bit in Control Status register to 1. This will allow the gauge to enter

the FULLSLEEP power mode after the transition to SLEEP power state is detected. In FullSleep mode less

power is consumed by disabling an oscillator circuit used by the communication engines. For HDQ

communication one host message will be dropped. For I2C communications the first I2C message will incur a 6 –

8 millisecond clock stretch while the oscillator is started and stabilized. A communication to the device in

FULLSLEEP will force the part back to the SLEEP mode.

SET_HIBERNATE: 0X0011

Instructs the fuel gauge to force the CONTROL_STATUS [HIBERNATE] bit to 1. This will allow the gauge to

enter the HIBERNATE power mode after the transition to SLEEP power state is detected. The [HIBERNATE] bit

is automatically cleared upon exiting from HIBERNATE mode.

CLEAR_HIBERNATE: 0X0012

Instructs the fuel gauge to force the CONTROL_STATUS [HIBERNATE] bit to 0. This will prevent the gauge from

entering the HIBERNATE power mode after the transition to SLEEP power state is detected. It can also be used

to force the gauge out of HIBERNATE mode.

SET_SHUTDOWN: 0X0013

Sets the CONTROL_STATUS [SHUTDOWN] bit to 1, thereby enabling the SE pin and CONTROL_STATUS [SE]

bit to change state. The Impedance Track algorithm controls the setting of the SE pin and [SE] bit, depending on

whether the conditions are met for fuel gauge shutdown or not.

CLEAR_SHUTDOWN: 0X0014

Disables the SE pin from changing state. The SE pin is left in a high-impedance state.

SEALED: 0X0020

Instructs the fuel gauge to transition from UNSEALED state to SEALED state. The fuel gauge should always be

set to SEALED state for use in end equipment.

IT_ENABLE: 0X0021

This command forces the fuel gauge to begin the Impedance Track™ algorithm, sets the active UpdateStatus

location to 0x01 and causes the [VOK] and [QEN] flags to be set in the CONTROL_STATUS register. [VOK] is

cleared if the voltages are not suitable for a Qmax update. Once set, [QEN] cannot be cleared. This command is

only available when the fuel gauge is UNSEALED.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

CAL_MODE: 0X0040

This command instructs the fuel gauge to enter calibration mode. This command is only available when the fuel

gauge is UNSEALED

RESET : 0X0041

This command instructs the fuel gauge to perform a full reset. This command is only available when the fuel

gauge is UNSEALED.

AtRate( ): 0x02/0x03

The AtRate( ) read-/write-word function is the first half of a two-function command set used to set the AtRate

value used in calculations made by the AtRateTimeToEmpty( ) function. The AtRate( ) units are in mA.

The AtRate( ) value is a signed integer, with negative values interpreted as a discharge current value. The

AtRateTimeToEmpty( ) function returns the predicted operating time at the AtRate value of discharge. The

default value for AtRate( ) is zero and will force AtRateTimeToEmpty( ) to return 65,535. Both the AtRate( ) and

AtRateTimeToEmpty( ) commands should only be used in NORMAL mode.

AtRateTimeToEmpty( ): 0x04/0x05

This read-only function returns an unsigned integer value of the predicted remaining operating time if the battery

is discharged at the AtRate( ) value in minutes with a range of 0 to 65,534. A value of 65,535 indicates AtRate( )

= 0. The fuel gauge updates AtRateTimeToEmpty( ) within 1 s after the system sets the AtRate( ) value. The fuel

gauge automatically updates AtRateTimeToEmpty( ) based on the AtRate( ) value every 1s. Both the AtRate( )

and AtRateTimeToEmpty( ) commands should only be used in NORMAL mode.

Temperature( ): 0x06/0x07

This read-only function returns an unsigned integer value of the battery temperature in units of 0.1K measured by

the fuel gauge.

Voltage( ): 0x08/0x09

This read-only function returns an unsigned integer value of the measured cell-pack voltage in mV with a range

of 0 to 6000 mV.

Flags( ): 0x0a/0x0b

This read-only function returns the contents of the gas-gauge status register, depicting the current operating

status.

Table 4. Flags Bit Definitions

bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0

High Byte OTC OTD – – CHG_INH XCHG FC CHG

Low Byte –– – – – – SOC1 SOCF DSG

OTC = Over-Temperature in Charge condition is detected. True when set

OTD = Over-Temperature in Discharge condition is detected. True when set

Charge Inhibit indicates the temperature is outside the range [Charge Inhibit Temp Low, Charge Inhibit Temp

CHG_INH = High]. True when set

Charge Suspend Alert indicates the temperature is outside the range [Suspend Temperature Low, Suspend

XCHG = Temperature High]. True when set

FC = Full-charged condition reached (RMFCC=1; Set FC_Set%=-1% when RMFCC=0). True when set

CHG = (Fast) charging allowed. True when set

SOC1 = State-of-Charge-Threshold 1 (SOC1 Set) reached. True when set

SOCF = State-of-Charge-Threshold Final (SOCF Set %) reached. True when set

DSG = Discharging detected. True when set

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

NominalAvailableCapacity( ): 0x0c/0x0d

This read-only command pair returns the uncompensated (less than C/20 load) battery capacity remaining. Units

are mAh.

FullAvailableCapacity( ): 0x0e/0x0f

This read-only command pair returns the uncompensated (less than C/20 load) capacity of the battery when fully

charged. Units are mAh. FullAvailableCapacity( ) is updated at regular intervals, as specified by the IT algorithm.

RemainingCapacity( ): 0x10/0x11

This read-only command pair returns the compensated battery capacity remaining. Units are mAh.

FullChargeCapacity( ): 0x12/13

This read-only command pair returns the compensated capacity of the battery when fully charged. Units are

mAh. FullChargeCapacity( ) is updated at regular intervals, as specified by the IT algorithm.

AverageCurrent( ): 0x14/0x15

This read-only command pair returns a signed integer value that is the average current flow through the sense

resistor. It is updated every 1 second. Units are mA.

TimeToEmpty( ): 0x16/0x17

This read-only function returns an unsigned integer value of the predicted remaining battery life at the present

rate of discharge, in minutes. A value of 65,535 indicates battery is not being discharged.

TimeToFull( ): 0x18/0x19

This read-only function returns an unsigned integer value of predicted remaining time until the battery reaches

full charge, in minutes, based upon AverageCurrent( ). The computation accounts for the taper current time

extension from the linear TTF computation based on a fixed AverageCurrent( ) rate of charge accumulation. A

value of 65,535 indicates the battery is not being charged.

StandbyCurrent( ): 0x1a/0x1b

This read-only function returns a signed integer value of the measured standby current through the sense

resistor. The StandbyCurrent( ) is an adaptive measurement. Initially it reports the standby current programmed

in Initial Standby, and after spending some time in standby, reports the measured standby current.

The register value is updated every 1 second when the measured current is above the Deadband Current and is

less than or equal to 2 x Initial Standby Current. The first and last values that meet this criteria are not

averaged in, since they may not be stable values. To approximate a 1 minute time constant, each new

StandbyCurrent( ) value is computed by taking approximate 93% weight of the last standby current and

approximate 7% of the current measured average current.

StandbyTimeToEmpty( ): 0x1c/0x1d

This read-only function returns an unsigned integer value of the predicted remaining battery life at the standby

rate of discharge, in minutes. The computation uses Nominal Available Capacity (NAC), the uncompensated

remaining capacity, for this computation. A value of 65,535 indicates battery is not being discharged.

MaxLoadCurrent( ): 0x1e/0x1f

This read-only function returns a signed integer value, in units of mA, of the maximum load conditions. The

MaxLoadCurrent( ) is an adaptive measurement which is initially reported as the maximum load current

programmed in Initial Max Load Current. If the measured current is ever greater than Initial Max Load

Current, then MaxLoadCurrent( ) updates to the new current. MaxLoadCurrent( ) is reduced to the average of

the previous value and Initial Max Load Current whenever the battery is charged to full after a previous

discharge to an SOC less than 50%. This prevents the reported value from maintaining an unusually high value.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

MaxLoadTimeToEmpty( ): 0x20/0x21

This read-only function returns an unsigned integer value of the predicted remaining battery life at the maximum

load current discharge rate, in minutes. A value of 65,535 indicates that the battery is not being discharged.

AvailableEnergy( ): 0x22/0x23

This read-only function returns an unsigned integer value of the predicted charge or energy remaining in the

battery. The value is reported in units of mWh.

AveragePower( ): 0x24/0x25

This read-word function returns an unsigned integer value of the average power of the current discharge. A value

of 0 indicates that the battery is not being discharged. The value is reported in units of mW.

TimeToEmptyAtConstantPower( ): 0x26/0x27

This read-only function returns an unsigned integer value of the predicted remaining operating time if the battery

is discharged at the AveragePower( ) value in minutes. A value of 65,535 indicates AveragePower( ) = 0. The

fuel gauge automatically updates TimeToEmptyatContantPower( ) based on the AveragePower( ) value every 1s.

CycleCount( ): 0x2a/0x2b

This read-only function returns an unsigned integer value of the number of cycles the battery has experienced

with a range of 0 to 65,535. One cycle occurs when accumulated discharge ≥CC Threshold.

StateOfCharge( ): 0x2c/0x2d

This read-only function returns an unsigned integer value of the predicted remaining battery capacity expressed

as a percentage of FullChargeCapacity( ), with a range of 0 to 100%.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

EXTENDED DATA COMMANDS

Extended commands offer additional functionality beyond the standard set of commands. They are used in the

same manner; however unlike standard commands, extended commands are not limited to 2-byte words. The

number of commands bytes for a given extended command ranges in size from single to multiple bytes, as

specified in Table 5. For details on the SEALED and UNSEALED states, see Section Access Modes.

Table 5. Extended Commands

NAME COMMAND CODE UNITS SEALED UNSEALED

ACCESS(1) (2) ACCESS(1) (2)

Reserved RSVD 0x34…0x3b N/A R R

DesignCapacity( ) DCAP 0x3c / 0x3d mAh R R

DataFlashClass( ) (2) DFCLS 0x3e N/A N/A R/W

DataFlashBlock( ) (2) DFBLK 0x3f N/A R/W R/W

BlockData( ) / Authenticate( ) (3) A/DF 0x40…0x53 N/A R/W R/W

BlockData( ) / AuthenticateCheckSum( ) (3) ACKS/DFD 0x54 N/A R/W R/W

BlockData( ) DFD 0x55…0x5f N/A R R/W

BlockDataCheckSum( ) DFDCKS 0x60 N/A R/W R/W

BlockDataControl( ) DFDCNTL 0x61 N/A N/A R/W

DeviceNameLength( ) DNAMELEN 0x62 N/A R R

DeviceName( ) DNAME 0x63...0x69 N/A R R

Reserved RSVD 0x6a...0x7f N/A R R

(1) SEALED and UNSEALED states are entered via commands to Control( ) 0x00/0x01

(2) In sealed mode, data flash CANNOT be accessed through commands 0x3e and 0x3f.

(3) The BlockData( ) command area shares functionality for accessing general data flash and for using Authentication. See section on

Authentication for more details.

DesignCapacity( ): 0x3c/0x3d

SEALED and UNSEALED Access: This command returns the value is stored in Design Capacity and is

expressed in mAh. This is intended to be the theoretical or nominal capacity of a new pack, but has no bearing

on the operation of the fuel gauge functionality.

DataFlashClass( ): 0x3e

UNSEALED Access: This command sets the data flash class to be accessed. The class to be accessed should

be entered in hexadecimal.

SEALED Access: This command is not available in SEALED mode.

DataFlashBlock( ): 0x3f

UNSEALED Access: This command sets the data flash block to be accessed. When 0x00 is written to

BlockDataControl( ),DataFlashBlock( ) holds the block number of the data flash to be read or written. Example:

writing a 0x00 to DataFlashBlock( ) specifies access to the first 32 byte block and a 0x01 specifies access to the

second 32 byte block, and so on.

SEALED Access: This command directs which data flash block will be accessed by the BlockData( ) command.

Writing a 0x00 to DataFlashBlock( ) specifies the BlockData( ) command will transfer authentication data. Issuing

a 0x01, 0x02 or 0x03 instructs the BlockData( ) command to transfer Manufacturer Info Block A, B, or C,

respectively.

BlockData( ): 0x40…0x5f

This command range is used to transfer data for data flash class access. This command range is the 32-byte

data block used to access Manufacturer Info Block A, B, or C. Manufacturer Info Block A is read only for the

sealed access. UNSEALED access is read/write.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

BlockDataChecksum( ): 0x60

The host system should write this value to inform the device that new data is ready for programming into the

specified data flash class and block.”

UNSEALED Access: This byte contains the checksum on the 32 bytes of block data read or written to data flash.

The least-significant byte of the sum of the data bytes written must be complemented ( [255 – x] , for x the

least-significant byte) before being written to 0x60.

SEALED Access: This byte contains the checksum for the 32 bytes of block data written to Manufacturer Info

Block A, B, or C. The least-significant byte of the sum of the data bytes written must be complemented ( [255 –

x] , for x the least-significant byte) before being written to 0x60.

BlockDataControl( ): 0x61

UNSEALED Access: This command is used to control data flash access mode. Writing 0x00 to this command

enables BlockData( ) to access general data flash. Writing a 0x01 to this command enables SEALED mode

operation of DataFlashBlock( ).

SEALED Access: This command is not available in SEALED mode.

DeviceNameLength( ): 0x62

UNSEALED and SEALED Access: This byte contains the length of the Device Name.

DeviceName( ): 0x63…0x69

UNSEALED and SEALED Access: This block contains the device name that is programmed in Device Name.

Reserved – 0x6a – 0x7f

DATA FLASH INTERFACE

Accessing the Data Flash

The bq27541 data flash is a non-volatile memory that contains bq27541 initialization, default, cell status,

calibration, configuration, and user information. The data flash can be accessed in several different ways,

depending on what mode the bq27541 is operating in and what data is being accessed.

Commonly accessed data flash memory locations, frequently read by a system, are conveniently accessed

through specific instructions, already described in Section Data Commands. These commands are available

when the bq27541 is either in UNSEALED or SEALED modes.

Most data flash locations, however, are only accessible in UNSEALED mode by use of the bq27541 evaluation

software or by data flash block transfers. These locations should be optimized and/or fixed during the

development and manufacture processes. They become part of a golden image file and can then be written to

multiple battery packs. Once established, the values generally remain unchanged during end-equipment

operation.

To access data flash locations individually, the block containing the desired data flash location(s) must be

transferred to the command register locations, where they can be read to the system or changed directly. This is

accomplished by sending the set-up command BlockDataControl( ) (0x61) with data 0x00. Up to 32 bytes of data

can be read directly from the BlockData( ) (0x40…0x5f), externally altered, then rewritten to the BlockData( )

command space. Alternatively, specific locations can be read, altered, and rewritten if their corresponding offsets

are used to index into the BlockData( ) command space. Finally, the data residing in the command space is

transferred to data flash, once the correct checksum for the whole block is written to BlockDataChecksum( )

(0x60).

Occasionally, a data flash CLASS will be larger than the 32-byte block size. In this case, the DataFlashBlock( )

command is used to designate which 32-byte block the desired locations reside in. The correct command

address is then given by 0x40 + offset modulo 32. For example, to access Terminate Voltage in the Gas

Gauging class, DataFlashClass( ) is issued 80 (0x50) to set the class. Because the offset is 48, it must reside in

the second 32-byte block. Hence, DataFlashBlock( ) is issued 0x01 to set the block offset, and the offset used to

index into the BlockData( ) memory area is 0x40 + 48 modulo 32 = 0x40 + 16 = 0x40 + 0x10 = 0x50.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

Reading and writing subclass data are block operations up to 32 bytes in length. If during a write the data length

exceeds the maximum block size, then the data is ignored.

None of the data written to memory are bounded by the bq27541 — the values are not rejected by the fuel

gauge. Writing an incorrect value may result in hardware failure due to firmware program interpretation of the

invalid data. The written data is persistent, so a power-on reset does resolve the fault.

MANUFACTURER INFORMATION BLOCKS

The bq27541 contains 96 bytes of user programmable data flash storage: Manufacturer Info Block A,

Manufacturer Info Block B,Manufacturer Info Block C. The method for accessing these memory locations is

slightly different, depending on whether the device is in UNSEALED or SEALED modes.

When in UNSEALED mode and when and 0x00 has been written to BlockDataControl( ), accessing the

Manufacturer Info Blocks is identical to accessing general data flash locations. First, a DataFlashClass( )

command is used to set the subclass, then a DataFlashBlock( ) command sets the offset for the first data flash

address within the subclass. The BlockData( ) command codes contain the referenced data flash data. When

writing the data flash, a checksum is expected to be received by BlockDataChecksum( ). Only when the

checksum is received and verified is the data actually written to data flash.

As an example, the data flash location for Manufacturer Info Block B is defined as having a Subclass = 58 and

an Offset = 32 through 63 (32 byte block). The specification of Class = System Data is not needed to address

Manufacturer Info Block B, but is used instead for grouping purposes when viewing data flash info in the

bq27541 evaluation software.

When in SEALED mode or when 0x01 BlockDataControl( ) does not contain 0x00, data flash is no longer

available in the manner used in UNSEALED mode. Rather than issuing subclass information, a designated

Manufacturer Information Block is selected with the DataFlashBlock( ) command. Issuing a 0x01, 0x02, or 0x03

with this command causes the corresponding information block (A, B, or C, respectively) to be transferred to the

command space 0x40…0x5f for editing or reading by the system. Upon successful writing of checksum

information to BlockDataChecksum( ), the modified block is returned to data flash. Note: Manufacturer Info

Block A is read-only when in SEALED mode.

ACCESS MODES

The bq27541 provides three security modes (FULL ACCESS, UNSEALED, and SEALED) that control data flash

access permissions according to Table 6.Data Flash refers to those data flash locations, specified in Table 7,

that are accessible to the user. Manufacture Information refers to the three 32-byte blocks.

Table 6. Data Flash Access

Security Mode Data Flash Manufacturer Information

FULL ACCESS R/W R/W

UNSEALED R/W R/W

SEALED None R (A); R/W (B,C)

Although FULL ACCESS and UNSEALED modes appear identical, only FULL ACCESS mode allows the

bq27541 to write access-mode transition keys.

SEALING/UNSEALING DATA FLASH

The bq27541 implements a key-access scheme to transition between SELAED, UNSEALED, and

FULL-ACCESS modes. Each transition requires that a unique set of two keys be sent to the bq27541 via the

Control( ) control command. The keys must be sent consecutively, with no other data being written to the

Control( ) register in between. Note that to avoid conflict, the keys must be different from the codes presented in

the CNTL DATA column of Table 2subcommands.

When in SEALED mode the [SS] bit of CONTROL_STATUS is set, but when the UNSEAL keys are correctly

received by the bq27541, the [SS] bit is cleared. When the full-access keys are correctly received then the

CONTROL_STATUS [FAS] bit is cleared.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

Both Unseal Key and Full-Access Key have two words and are stored in data flash. The first word is Key 0 and

the second word is Key 1. The order of the keys sent to bq27541 are Key 1 followed by Key 0. The order of the

bytes for each key entered through the Control( ) command is the reverse of what is read from the part. For an

example, if the Unseal Key is 0x56781234, key 1 is 0x1234 and key 0 is 0x5678. Then Control( ) should supply

0x3412 and 0x7856 to unseal the part. The Unseal key and the FULL-ACCESS key cap only be updated when

in FULL-ACCESS mode.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

DATA FLASH SUMMARY

Table 7 summarizes the data flash locations available to the user, including their default, minimum, and

maximum values.

Table 7. Data Flash Summary

Class Subclass Subclass Offset Name Data Min Max Value Default Value Units

ID Type Value

Configuration 2 Safety 0 OT Chg I2 0 1200 550 0.1°C

Configuration 2 Safety 2 OT Chg Time U1 0 60 2 s

Configuration 2 Safety 3 OT Chg Recovery I2 0 1200 500 0.1°C

Configuration 2 Safety 5 OT Dsg I2 0 1200 600 0.1°C

Configuration 2 Safety 7 OT Dsg Time U1 0 60 2 s

Configuration 2 Safety 8 OT Dsg Recovery I2 0 1200 550 0.1°C

Configuration 32 Charge Inhibit Config 0 Charge Inhibit Temp Low I2 –400 1200 0 0.1°C

Configuration 32 Charge Inhibit Config 2 Charge Inhibit Temp High I2 –400 1200 450 0.1°C

Configuration 32 Charge Inhibit Config 4 Temp Hys I2 0 100 50 0.1°C

Configuration 34 Charge 2 Charging Voltage I2 0 20,000 4200 mV

Configuration 34 Charge 4 Delta Temperature I2 0 500 50 0.1°C

Configuration 34 Charge 6 Suspend Temperature Low I2 –400 1200 -50 0.1°C

Configuration 34 Charge 8 Suspend Temperature High I2 –400 1200 550 0.1°C

Configuration 36 Charge Termination 2 Taper Current I2 0 1000 100 mA

Configuration 36 Charge Termination 4 Minimum Taper Charge I2 0 1000 25 0.01mAh

Configuration 36 Charge Termination 6 Taper Voltage I2 0 1000 100 mV

Configuration 36 Charge Termination 8 Current Taper Window U1 0 60 40 s

Configuration 36 Charge Termination 9 Terminate Charge Alarm Set % I1 -1 100 99 %

Configuration 36 Charge Termination 10 Terminate Charge Alarm Clear % I1 -1 100 95 %

Configuration 36 Charge Termination 11 Full Charge Set % I1 -1 100 100 %

Configuration 36 Charge Termination 12 Full Charge Clear % I1 -1 100 98 %

Configuration 48 Data 0 Remaining Capacity Alarm I2 0 70 100 mAh

Configuration 48 Data 8 Initial Standby Current I1 –256 0 –10 mA

Configuration 48 Data 9 Initial Max Load Current I2 –32,767 0 –500 mA

Configuration 48 Data 17 Cycle Count U2 0 65535 0 Count

Configuration 48 Data 19 CC Threshold I2 100 32,767 900 mAh

Configuration 48 Data 23 Design Capacity I2 0 65,535 1000 mAh

Configuration 48 Data 39 Device Name S8 x x bq27541 –

Configuration 49 Discharge 0 SOC1 Set Threshold U1 0 255 150 mAh

Configuration 49 Discharge 1 SOC1 Clear U1 0 255 175 mAh

Configuration 49 Discharge 2 SOCF Set Threshold U1 0 255 75 mAh

Configuration 49 Discharge 3 SOCF Clear U1 0 255 100 mAh

System Data 58 Manufacturer Info 0–31 Block A [0–31] H1 0x00 0xff 0x00 –

System Data 58 Manufacturer Info 32–63 Block B [0–31] H1 0x00 0xff 0x00 –

System Data 58 Manufacturer Info 64–95 Block C [0–31] H1 0x00 0xff 0x00 –

Configuration 64 Registers 0 Pack Configuration H2 0x0000 0xffff 0x0135 –

Configuration 68 Power 0 Flash Update OK Voltage I2 0 4200 2800 mV

Configuration 68 Power 7 Sleep Current I2 0 100 10 mA

Configuration 68 Power 16 Hibernate Current U2 0 700 8 mA

Configuration 68 Power 18 Hibernate Voltage U2 2400 3000 2550 mV

Configuration 68 Power 20 Full Sleep Wait Time U1 0 255 0 s

Gas Gauging 80 IT Cfg 0 Load Select U1 0 255 1 –

Gas Gauging 80 IT Cfg 1 Load Mode U1 0 255 0 –

Gas Gauging 80 IT Cfg 48 Terminate Voltage I2 2800 3700 3000 mV

Gas Gauging 80 IT Cfg 65 User Rate-mW I2 0 14,000 0 mW

Gas Gauging 80 IT Cfg 67 Reserve Cap-mAh I2 0 9000 0 mAh

Gas Gauging 80 IT Cfg 69 Reserve Cap-mWh I2 0 14,000 0 mWh

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

Table 7. Data Flash Summary (continued)

Class Subclass Subclass Offset Name Data Min Max Value Default Value Units

ID Type Value

Gas Gauging 81 Current Thresholds 0 Dsg Current Threshold I2 0 2000 60 mA

Gas Gauging 81 Current Thresholds 2 Chg Current Threshold I2 0 2000 75 mA

Gas Gauging 81 Current Thresholds 4 Quit Current I2 0 1000 40 mA

Gas Gauging 81 Current Thresholds 6 Dsg Relax Time U2 0 8191 1800 s

Gas Gauging 81 Current Thresholds 8 Chg Relax Time U1 0 255 60 s

Gas Gauging 81 Current Thresholds 9 Quit Relax Time U1 0 63 1 s

Gas Gauging 82 State 0 Qmax Cell0 I2 0 32,767 1000 mAh

Gas Gauging 82 State 2 Qmax I2 0 32,767 1500 mAh

Gas Gauging 82 State 4 Cycle Count U2 0 65,535 0 –

Gas Gauging 82 State 6 Update Status H1 0x00 0x03 0x00 –

Gas Gauging 82 State 9 Avg I Last Run I2 –32,768 32,767 -299 mA

Gas Gauging 82 State 11 Avg P Last Run I2 –32,768 32,767 -1131 mAh

Ra Tables 88 Pack Ra0 0–31 See (1)

Ra Tables 89 Pack Ra0x 0–31

Calibration 104 Data 0 CC Gain F4(2) 0.1 47 10(3) mΩ

Calibration 104 Data 4 CC Delta F4(2) 4.7 188 10(3) mΩ

Calibration 104 Data 8 CC Offset I2 –2.4 24 –0.088(3) mV

Calibration 104 Data 10 Board Offset I1 –128 127 0 mV

Calibration 104 Data 11 Int Temp Offset I1 –128 127 0 0.1°C

Calibration 104 Data 12 Ext Temp Offset I1 –128 127 0 0.1°C

Calibration 104 Data 13 Pack V Offset I1 –128 127 0 mV

Calibration 107 Current 1 Deadband U1 0 255 5 mA

Security 112 Codes 0 Unseal Key H4 0x0000 0xffffffff 0x36720414 –

Security 112 Codes 4 Full-Access Key H4 0x0000 0xffffffff 0xffffffff –

Security 112 Codes 8 Authentication Key 3 H4 0x0000 0xffffffff 0x01234567 –

Security 112 Codes 12 Authentication Key 2 H4 0x0000 0xffffffff 89ABCDEF –

Security 112 Codes 16 Authentication Key 1 H4 0x0000 0xffffffff FEDCBA98 –

Security 112 Codes 20 Authentication Key 0 H4 0x0000 0xffffffff 76543210 –

(1) Encoded battery profile information created by bqEasy software

(2) Not IEEE floating point

(3) Display as the value EVSW displayed. Data Flash value is different.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

FUNCTIONAL DESCRIPTION

FUEL GAUGING

The bq27541 measures the cell voltage, temperature, and current to determine battery SOC. The bq27541

monitors charge and discharge activity by sensing the voltage across a small-value resistor (5 mΩto 20 mΩtyp.)

between the SRP and SRN pins and in series with the cell. By integrating charge passing through the battery,

the battery’s SOC is adjusted during battery charge or discharge.

The total battery capacity is found by comparing states of charge before and after applying the load with the

amount of charge passed. When an application load is applied, the impedance of the cell is measured by

comparing the OCV obtained from a predefined function for present SOC with the measured voltage under load.

Measurements of OCV and charge integration determine chemical state of charge and chemical capacity

(Qmax). The initial Qmax values are taken from a cell manufacturers' data sheet multiplied by the number of

parallel cells. It is also used for the value in Design Capacity. The bq27541 acquires and updates the

battery-impedance profile during normal battery usage. It uses this profile, along with SOC and the Qmax value,

to determine FullChargeCapacity( ) and StateOfCharge( ), specifically for the present load and temperature.

FullChargeCapacity( ) is reported as capacity available from a fully charged battery under the present load and

temperature until Voltage( ) reaches the Terminate Voltage.NominalAvailableCapacity( ) and

FullAvailableCapacity( ) are the uncompensated (no or light load) versions of RemainingCapacity( ) and

FullChargeCapacity( ) respectively.

The bq27541 has two flags accessed by the Flags( ) function that warns when the battery’s SOC has fallen to

critical levels. When RemainingCapacity( ) falls below the first capacity threshold, specified in SOC1 Set

Threshold, the [SOC1] (State of Charge Initial) flag is set. The flag is cleared once RemainingCapacity( ) rises

above SOC1 Set Threshold. All units are in mAh.

When RemainingCapacity( ) falls below the second capacity threshold, SOCF Set Threshold, the [SOCF] (State

of Charge Final) flag is set, serving as a final discharge warning. If SOCF Set Threshold = –1, the flag is

inoperative during discharge. Similarly, when RemainingCapacity( ) rises above SOCF Clear Threshold and the

[SOCF] flag has already been set, the [SOCF] flag is cleared. All units are in mAh.

IMPEDANCE TRACK™ VARIABLES

The bq27541 has several data flash variables that permit the user to customize the Impedance Track™ algorithm

for optimized performance. These variables are dependent upon the power characteristics of the application as

well as the cell itself.

Load Mode

Load Mode is used to select either the constant-current or constant-power model for the Impedance Track™

algorithm as used in Load Select (see Load Select). When Load Mode is 0, the Constant Current Model is

used (default). When 1, the Constant Power Model is used. The [LDMD] bit of CONTROL_STATUS reflects the

status of Load Mode.

Load Select

Load Select defines the type of power or current model to be used to compute load-compensated capacity in the

Impedance Track™ algorithm. If Load Mode =0(Constant Current), then the options presented in Table 8 are

available.

Table 8. Constant-Current Model Used when Load Mode = 0

LoadSelect Value Current Model Used

0Average discharge current from previous cycle: There is an internal register that records the average discharge current through each

entire discharge cycle. The previous average is stored in this register.

1(default) Present average discharge current: This is the average discharge current from the beginning of this discharge cycle until present time.

2Average current: based off the AverageCurrent( )

3Current: based off of a low-pass-filtered version of AverageCurrent( ) (t= 14s)

4Design capacity / 5: C Rate based off of Design Capacity /5 or a C / 5 rate in mA.

5AtRate (mA): Use whatever current is in AtRate( )

6User_Rate-mA: Use the value in User_Rate( ). This gives a completely user-configurable method.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

If Load Mode =1(Constant Power) then the following options are available:

Table 9. Constant-Power Model Used When Load Mode = 1

LoadSelect Value Power Model Used

0 (default) Average discharge power from previous cycle: There is an internal register that records the average discharge power through each

entire discharge cycle. The previous average is stored in this register.

1Present average discharge power: This is the average discharge power from the beginning of this discharge cycle until present time.

2Average current × voltage: based off the AverageCurrent( ) and Voltage( ).

3Current × voltage: based off of a low-pass-filtered version of AverageCurrent( ) (t= 14s) and Voltage( )

4Design energy / 5: C Rate based off of Design Energy /5 or a C / 5 rate in mA .

5AtRate (10 mW): Use whatever value is in AtRate( ).

6User_Rate-10mW: Use the value in. User_Rate( ) mW. This gives a completely user- configurable method.

Reserve Cap-mAh

Reserve Cap-mAh determines how much actual remaining capacity exists after reaching 0

RemainingCapacity( ), before Terminate Voltage is reached. A no-load rate of compensation is applied to this

reserve.

Reserve Cap-mWh

Reserve Cap-mWh determines how much actual remaining capacity exists after reaching 0 AvailableEnergy( ),

before Terminate Voltage is reached. A no-load rate of compensation is applied to this reserve capacity.

Dsg Current Threshold

This register is used as a threshold by many functions in the bq27541 to determine if actual discharge current is

flowing into or out of the cell. The default for this register should be sufficient for most applications. This threshold

should be set low enough to be below any normal application load current but high enough to prevent noise or

drift from affecting the measurement.

Chg Current Threshold

This register is used as a threshold by many functions in the bq27541 to determine if actual charge current is

flowing into or out of the cell. The default for this register should be sufficient for most applications. This threshold

should be set low enough to be below any normal charge current but high enough to prevent noise or drift from

affecting the measurement.

Quit Current, Dsg Relax Time, Chg Relax Time, and Quit Relax Time

The Quit Current is used as part of the Impedance Track™ algorithm to determine when the bq27541 enters

relaxation mode from a current flowing mode in either the charge direction or the discharge direction. The value

of Quit Current is set to a default value that should be above the standby current of the system.

Either of the following criteria must be met to enter relaxation mode:

1. | AverageCurrent( ) |<|Quit Current | for Dsg Relax Time.

2. | AverageCurrent( ) |<|Quit Current | for Chg Relax Time.

After about 30 minutes in relaxation mode, the bq27541 attempts to take accurate OCV readings. An additional

requirement of dV/dt < 4 mV/sec is required for the bq27541 to perform Qmax updates. These updates are used

in the Impedance Track™ algorithms. It is critical that the battery voltage be relaxed during OCV readings to and

that the current is not be higher than C/20 when attempting to go into relaxation mode.

Quit Relax Time specifies the minimum time required for AverageCurrent( ) to remain above the QuitCurrent

threshold before exiting relaxation mode.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

Qmax

Qmax contains the maximum chemical capacity of the active cell profiles, and is determined by comparing states

of charge before and after applying the load with the amount of charge passed. They also correspond to capacity

at low rate of discharge, such as C/20 rate. For high accuracy, this value is periodically updated by the bq27541

during operation. Based on the battery cell capacity information, the initial value of chemical capacity should be

entered in Qmax field. The Impedance Track™ algorithm will update this value and maintain it in the Pack

profile.

Update Status

Bit 0 (0x01) of the Update Status register indicates that the bq27541 has learned new Qmax parameters and is

accurate. The remaining bits are reserved. Bits 0 is a status bit set by the bq27541. Bit 0 should never be

modified except when creating a golden image file as explained in the application note Preparing Optimized

Default Flash Constants for specific Battery Types (SLUA334.pdf). Bit 0 is updated as needed by the bq27541.

Avg I Last Run

The bq27500 logs the current averaged from the beginning to the end of each discharge cycle. It stores this

average current from the previous discharge cycle in this register. This register should never need to be

modified. It is only updated by the bq27541 when required.

Avg P Last Run

The bq27541 logs the power averaged from the beginning to the end of each discharge cycle. It stores this

average power from the previous discharge cycle in this register. To get a correct average power reading the

bq27541 continuously multiplies instantaneous current times Voltage( ) to get power. It then logs this data to

derive the average power. This register should never need to be modified. It is only updated by the bq27541

when required.

Delta Voltage

The bq27541 stores the maximum difference of Voltage( ) during short load spikes and normal load, so the

Impedance Track™ algorithm can calculate remaining capacity for pulsed loads. It is not recommended to

change this value.

Default Ra and Ra Tables

These tables contain encoded data and, with the exception of the Default Ra Tables, are automatically updated

during device operation. No user changes should be made except for reading/writing the values from a

prelearned pack (part of the process for creating golden image files).

DETAILED PIN DESCRIPTIONS

System Shutdown Enable (SE Pin)

If the CONTROL_STATUS[SHUTDOWN] has been set, bq27541 will immediately pull the SE pin low at POR.

The fuel gauge can be made to power-off through an external circuit when it releases the SE pin to high

impedance. With an external circuit, this feature is useful to shutdown the fuel gauge in a deeply discharged

battery to protect the battery. The SE pin is released to open drain state when the gauge enters HIBERNATE

mode with the CONTROL_STATUS[HIBERNATE] and [SHUTDOWN] bits set.

The Pack Configuration Register

Some bq27541 pins are configured via the Pack Configuration data flash register, as indicated in Table 10. This

is located at subclass = 64, offset = 0.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

Table 10. Pack Configuration Bit Definition

bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0

High Byte RESCAP – – – – IWAKE RSNS1 RSNS0

Low Byte – – SLEEP RMFCC SE_PU SE_POL – TEMPS

RESCAP = No-load rate of compensation is applied to the reserve capacity calculation. True when set. Default is 0.

IWAKE/RSNS1/RSNS0 = These bits configure the current wake function (see Table 11). Default is 0/0/1.

SLEEP = The fuel gauge can enter sleep, if operating conditions allow. True when set. Default is 1.

RMFCC = RM is updated with the value from FCC, on valid charge termination. True when set. Default is 1.

SE_PU = Pull-up enable for SE pin. True when set (push-pull). Default is 0.

SE_POL = Polarity bit for SE pin. SE is active low when clear. Default is 1 (makes SE high when gauge is ready for

shutdown).

TEMPS = Selects external thermistor for Temperature( ) measurements. True when set. Default is 1.

TEMPERATURE MEASUREMENT AND THE TS INPUT

The bq27541 measures battery temperature via the TS input, in order to supply battery temperature status

information to the fuel gauging algorithm and charger-control sections of the gauge. Alternatively, the gauge can

also measure internal temperature via its on-chip temperature sensor, but only if the [TEMPS] bit of Pack

Configuration register is cleared.

Regardless of which sensor is used for measurement, a system processor can request the current battery

temperature by calling the Temperature( ) function (see Section Standard Data Commands, for specific

information).

The thermistor circuit requires the use of an external 10Kohm thermistor with negative temperature coefficients,

such as Semetic 103AT-type thermistor that connects between the Vcc and TS pins. Additional circuit

information for connecting this thermistor to the bq27541 is shown in Section 4, Reference Schematic.

OVERTEMPERATURE INDICATION

2.3.1 Overtemperature: Charge

If during charging, Temperature( ) reaches the threshold of OT Chg for a period of OT Chg Time and

AverageCurrent( ) > Chg Current Threshold, then the [OTC] bit of Flags( ) is set. When Temperature( ) falls to

OT Chg Recovery, the [OTC] of Flags( ) is reset.

If OT Chg Time = 0, the feature is completely disabled.

Overtemperature: Discharge

If during discharging, Temperature( ) reaches the threshold of OT Dsg for a period of OT Dsg Time, and

AverageCurrent( ) ≤-Dsg Current Threshold, then the [OTD] bit of Flags( ) is set. When Temperature( ) falls to

OT Dsg Recovery, the [OTD] bit of Flags( ) is reset.

If OT Dsg Time = 0, the feature is completely disabled.

CHARGE-TERMINATION/-INHIBIT INDICATORS

Detection Charge Termination

For proper bq27541 operation, the cell charging voltage must be specified by the user. The default value for this

variable is in the data flash Charging Voltage.

The bq27541 detects charge termination when (1) during 2 consecutive periods of Current Taper Window, the

AverageCurrent( ) is < Taper Current, (2) during the same periods, the accumulated change in capacity >

0.25mAh / Current Taper Window, and (3) Voltage( ) > Charging Voltage – Taper Voltage. When this occurs,

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

the [CHG] bit of Flags( ) is cleared. Also, if the [RMFCC] bit of Pack Configuration is set, and

RemainingCapacity( ) is set equal to FullChargeCapacity( ). When TCA_Set is set to -1, it disables the use of the

charger alarm threshold. In that case, TerminateCharge is set when the taper condition is detected. When

FC_Set is set to -1, it disables the use of the full charge detection threshold. In that case, FullCharge is not set

until the taper condition is met.

Charge Inhibit

The bq27541 can indicate when battery temperature has fallen below or risen above predefined thresholds

(Charge Inhibit Temp Low and Charge Inhibit Temp High, respectively). In this mode, the [CHG_INH] of

Flags( ) is made high to indicate this condition, and is returned to its low state, once battery temperature returns

to the range [Charge Inhibit Temp Low + Temp Hys,Charge Inhibit Temp High – Temp Hys].

POWER MODES

The bq27500 has three power modes: NORMAL, SLEEP, and HIBERNATE. In NORMAL mode, the bq27541 is

fully powered and can execute any allowable task. In SLEEP mode the fuel gauge exists in a reduced-power

state, periodically taking measurements and performing calculations. Finally, in HIBERNATE mode, the fuel

gauge is in a low power state, but can be awaken by communication or certain I/O activity.

The relationship between these modes is shown in Figure 3.

NORMAL Mode

The fuel gauge is in NORMAL Mode when not in any other power mode. During this mode, AverageCurrent( ),

Voltage( ) and Temperature( ) measurements are taken, and the interface data set is updated. Decisions to

change states are also made. This mode is exited by activating a different power mode.

Because the gauge consumes the most power in NORMAL mode, the Impedance Track™ algorithm minimizes

the time the fuel gauge remains in this mode.

SLEEP Mode

SLEEP mode is entered automatically if the feature is enabled (Pack Configuration [SLEEP]) = 1) and

AverageCurrent( ) is below the programmable level Sleep Current. Once entry into SLEEP mode has been

qualified, but prior to entering it, the bq27541 performs an ADC autocalibration to minimize offset.

While in SLEEP mode, the fuel gauge can suspend serial communications as much as 4ms by holding the comm

line(s) low. This delay is necessary to correctly process host communication, since the fuel gauge processor is

mostly halted in SLEEP mode.

During the SLEEP mode, bq27541 periodically takes data measurements and updates its data set. However, a

majority of its time is spent in an idle condition.

The bq27541 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) rises above

Sleep Current, or (2) a current in excess of IWAKE through RSENSE is detected.

FULLSLEEP Mode

FULLSLEEP mode is entered automatically if the feature is enabled by setting the Pack Configuration

[FULLSLEEP] bit in the Control Status register when the bq27541 is in SLEEP mode. The gauge exits the

FULLSLEEP mode when there is any communication activity. Therefore, the execution of SET_FULLSLEEP sets

[FULLSLEEP] bit, but EVSW might still display the bit clear. The FULLSLEEP mode can be verified by

measuring the current consumption of the gauge. In this mode, the high frequency oscialliator is turned off. The

power consumption is further reduced in this mode compared to the SLEEP mode.

FULLSLEEP mode can also be entered by set the Full Sleep Wait Time to be a number larger than 0. The

FULLSLEEP will be entered when the timer counts down to 0. This feature is disabled when the data flash is set

as 0.

During FULLSLEEP mode, the bq27541 periodically takes data measurements and updates its data set.

However, a majority of its time is spent in an idle condition.

The bq27541 exits SLEEP if any entry condition is broken, specifically when (1) AverageCurrent( ) rises above

Sleep Current, or (2) a current in excess of IWAKE through RSENSE is detected.

Product Folder Link(s): bq27541

Exit From SLEEP

Pack Configuration [SLEEP] = 0

| AverageCurrent( ) | >Sleep Current

Current is Detected above IWAKE

Exit From SLEEP

(Host has set Control Status

[HIBERNATE] = 1

VCELL <Hibernate Voltage

Fuelgauginganddata

updated every 1s

NORMAL

Fuel gauging and data

updated every 20 seconds

SLEEP

Disableallbq27541

subcircuits except GPIO.

HIBERNATE

Entry to SLEEP

Pack Configuration [SLEEP] = 1

AND

| AverageCurrent( ) |≤Sleep Current

Wakeup From HIBERNATE

Communication Activity

AND

Comm address is NOT for bq27541

Exit From HIBERNATE

VCELL < POR threshold

POR

Exit From WAIT_HIBERNATE

Cell relaxed

AND

| AverageCurrent() | < Hibernate

Current

Cell relaxed

AND

VCELL <Hibernate Voltage

System Shutdown

Exit From WAIT_HIBERNATE

Host must set Control Status

[HIBERNATE] = 0

AND

VCELL > Hibernate Voltage

Exit From HIBERNATE

Communication Activity

AND Comm address is for bq27541

bq27541 clears Control Status

[HIBERNATE] = 0

Recommend Host also set Control

Status [HIBERNATE] = 0

WAIT_HIBERNATE

Fuel gauging and data

updated every 20 seconds

In low power state of SLEEP

mode. Gas gauging and data

updated every 20 seconds

FULLSLEEP

System Sleep

FULLSLEEP Count Down

WAITFULLSLEEP

Entry to FULLSLEEP

Host must set Control Status

[FULLSLEEP] = 1

Exit From WAITFULLSLEEP

Any Communication Cmd

Entry to WAITFULLSLEEP

Full Sleep Wait Time > 0

Entry to FULLSLEEP

Count <1

FULLSLEEP

Exit From

Any

Communication

Cmd

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

While in FULLSLEEP mode, the fuel gauge can suspend serial communications as much as 4ms by holding the

comm line(s) low. This delay is necessary correctly process host communication, since the fuel gauge processor

is mostly halted in SLEEP mode.

Figure 3. Power Mode Diagram

HIBERNATE Mode

HIBERNATE mode should be used when the host system needs to enter a low-power state, and minimal gauge

power consumption is required. This mode is ideal when the host is set to its own HIBERNATE, SHUTDOWN, or

OFF modes. The fuel gauge can enter HIBERNATE due to either low cell voltage or low load current.

– HIBERNATE due to the cell voltage. When the cell voltage drops below the Hibernate Voltage and a valid OCV

measurement has been taken, the fuel gauge enters HIBERNATE mode. The [HIBERNATE] bit of the

CONTROL register has no impact for the fuel gauge to enter the HIBERNATE mode. If the [SHUTDOWN] bit of

CONTROL _STATUS is also set, the SE pin will be released, thereby allowing an optional external circuit to

remove power from the gauge LDO.

– HIBERNATE due to the load current. If the fuel gauge enters the HIBERNATE mode due to the load current,

the [HIBERNATE] bit of the CONTROL_STATUS register must be set. The gauge waits to enter HIBERNATE

mode until it has taken a valid OCV measurement and the magnitude of the average cell current has fallen below

Hibernate Current.

Product Folder Link(s): bq27541

Store

checksum

ActiveRAM

changed?

Generatenew

checksumvalue

YES

Generate Active

RAMchecksum

value

DotheChecksum

ValuesMatch?

Re-initializeall

RAM

YES

DEVICERESET

Stored

checksum

NORMAL

OPERATION

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

The gauge will remain in HIBERNATE mode until communication activity appears on the communication lines

Upon exiting HIBERNATE mode, the [HIBERNATE] bit of CONTROL_STATUS is cleared.

Because the fuel gauge is dormant in HIBERNATE mode, the battery should not be charged or discharged in this

mode, because any changes in battery charge status will not be measured. If necessary, the host equipment can

draw a small current (generally infrequent and less than 1mA, for purposes of low-level monitoring and updating);

however, the corresponding charge drawn from the battery will not be logged by the gauge. Once the gauge

exits to NORMAL mode, the IT algorithm will re-establish the correct battery capacity, regardless of the total

charge drawn in HIBERNATE mode.

If a charger is attached, the host should immediately take the fuel gauge out of HIBERNATE mode before

beginning to charge the battery. Charging the battery in HIBERNATE mode will result in a notable gauging error

that will take several hours to correct.

POWER CONTROL

Reset Functions

When the bq27541 detects a software reset ([RESET] bit of Control( ) initiated), it determines the type of reset

and increments the corresponding counter. This information is accessible by issuing the command Control( )

function with the RESET_DATA subcommand.

As shown in Figure 4 if a partial reset was detected, a RAM checksum is generated and compared against the

previously stored checksum. If the checksum values do not match, the RAM is reinitialized (a Full Reset). The

stored checksum is updated every time RAM is altered.

Figure 4. Partial Reset Flow Diagram

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

Wake-Up Comparator

The wake up comparator is used to indicate a change in cell current while the bq27541 is in either SLEEP or

HIBERNATE modes. Pack Configuration uses bits [RSNS1-RSNS0] to set the sense resistor selection.

Operation Configuration also uses the [IWAKE] bit to select one of two possible voltage threshold ranges for

the given sense resistor selection. An internal interrupt is generated when the threshold is breached in either

charge or discharge directions. Setting both [RSNS1] and [RSNS0] to 0 disables this feature..

Table 11. IWAKE Threshold Settings(1)

RSNS1 RSNS0 IWAKE Vth(SRP-SRN)

0 0 0 Disabled

0 0 1 Disabled

0 1 0 +1.25 mV or –1.25 mV

0 1 1 +2.5 mV or –2.5 mV

1 0 0 +2.5 mV or –2.5 mV

1 0 1 +5 mV or –5 mV

1 1 0 +5 mV or –5 mV

1 1 1 +10 mV or –10 mV

(1) The actual resistance value vs. the setting of the sense resistor is not important just the actual voltage

threshold when calculating the configuration.

Flash Updates

Data Flash can only be updated if Voltage( ) ≥Flash Update OK Voltage. Flash programming current can cause

an increase in LDO dropout. The value of Flash Update OK Voltage should be selected such that the bq27541

Vcc voltage does not fall below its minimum of 2.4V during Flash write operations.

AUTOCALIBRATION

The bq27541 provides an autocalibration feature that will measure the voltage offset error across SRP and SRN

from time-to-time as operating conditions change. It subtracts the resulting offset error from normal sense

resistor voltage, VSR, for maximum measurement accuracy.

Autocalibration of the ADC begins on entry to SLEEP mode, except if Temperature( ) is ≤5°C or Temperature( )

≥45°C.

The fuel gauge also performs a single offset when (1) the condition of AverageCurrent( ) ≤≤ 100mA and (2)

{voltage change since last offset calibration ≥256mV} or {temperature change since last offset calibration is

greater than 80°C for ≥60s}.

Capacity and current measurements will continue at the last measured rate during the offset calibration when

these measurements cannot be performed. If the battery voltage drops more than 32mV during the offset

calibration, the load current has likely increased considerably; hence, the offset calibration will be aborted.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

COMMUNICATIONS

AUTHENTICATION

The bq27541 can act as a SHA-1/HMAC authentication slave by using its internal engine. Sending a 160-bit

SHA-1 challenge message to the bq27541 will cause the gauge to return a 160-bit digest, based upon the

challenge message and a hidden, 128-bit plain-text authentication key. If this digest matches an identical one

generated by a host or dedicated authentication master, and when operating on the same challenge message

and using the same plain text keys, the authentication process is successful.

KEY PROGRAMMING (DATA FLASH KEY)

By default, the bq27541 contains a default plain-text authentication key of

0x0123456789ABCDEFFEDCBA9876543210. This default key is intended for development purposes. It should

be changed to a secret key and the part immediately sealed, before putting a pack into operation. Once written, a

new plain-text key cannot be read again from the fuel gauge while in SEALED mode.

Once the bq27541 is UNSEALED, the authentication key can be changed from its default value by writing to the

Authentication( ) Extended Data Command locations. A 0x00 is written to BlockDataControl( ) to enable the

authentication data commands. The bq27541 is now prepared to receive the 16-byte plain-text key, which must

begin at command location 0x40 and ending at 0x4f. Once written, the key is accepted when a successful

checksum for the key has been written to AuthenticateChecksum( ). The gauge can then be SEALED again.

KEY PROGRAMMING (THE SECURE MEMORY KEY)

As the name suggests, the bq27541 secure-memory authentication key is stored in the secure memory of the

bq27541. If a secure-memory key has been established, only this key can be used for authentication challenges

(the programmable data flash key is not available). The selected key can only be established/programmed by

special arrangements with TI, using the TI’s Secure B-to-B Protocol. The secure-memory key can never be

changed or read from the bq27541.

EXECUTING AN AUTHENTICATION QUERY

To execute an authentication query in UNSEALED mode, a host must first write 0x01 to the BlockDataControl( )

command, to enable the authentication data commands. If in SEALED mode, 0x00 must be written to

DataFlashBlock( ), instead.

Next, the host writes a 20-byte authentication challenge to the Authenticate( ) address locations (0x40 through

0x53). After a valid checksum for the challenge is written to AuthenticateChecksum( ), the bq27541 uses the

challenge to perform it own the SHA-1/HMAC computation, in conjunction with its programmed keys. The

resulting digest is written to AuthenticateData( ), overwriting the pre-existing challenge. The host may then read

this response and compare it against the result created by its own parallel computation.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

HDQ SINGLE-PIN SERIAL INTERFACE

The HDQ interface is an asynchronous return-to-one protocol where a processor sends the command code to

the bq27541. With HDQ, the least significant bit (LSB) of a data byte (command) or word (data) is transmitted

first. Note that the DATA signal on pin 12 is open-drain and requires an external pull-up resistor. The 8-bit

command code consists of two fields: the 7-bit HDQ command code (bits 0–6) and the 1-bit R/W field (MSB

bit 7). The R/W field directs the bq27541 either to

• Store the next 8 or 16 bits of data to a specified register or

• Output 8 or 16 bits of data from the specified register

The HDQ peripheral can transmit and receive data as either an HDQ master or slave.

The return-to-one data bit frame of HDQ consists of three distinct sections. The first section is used to start the

transmission by either the host or by the bq27541 taking the DATA pin to a logic-low state for a time t(STRH,B).

The next section is for data transmission, where the data are valid for a time t(DSU), after the negative edge used

to start communication. The data are held until a time t(DV), allowing the host or bq27541 time to sample the data

bit. The final section is used to stop the transmission by returning the DATA pin to a logic-high state by at least a

time t(SSU), after the negative edge used to start communication. The final logic-high state is held until the end of

t(CYCH,B), allowing time to ensure the transmission was stopped correctly. The timing for data and break

communication are given in the HDQ characteristics section.

HDQ serial communication is normally initiated by the host processor sending a break command to the bq27541.

A break is detected when the DATA pin is driven to a logic-low state for a time t(B) or greater. The DATA pin

should then be returned to its normal ready high logic state for a time t(BR). The bq27541 is now ready to receive

information from the host processor.

The bq27541 is shipped in the I2C mode. TI provides tools to enable the HDQ peripheral.

Product Folder Link(s): bq27541

SADDR[6:0] 0 A CMD[7:0] ADATA[7:0] A P S ADDR[6:0] 1 A DATA[7:0] N P

SADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA[7:0] N P

SADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA[7:0] A... DATA[7:0] N P

(d)

(c)

(a) (b)

HostGenerated FuelGaugeGenerated

SADDR[6:0] 0 A CMD[7:0] ADATA[7:0] A P

SADDR[6:0] 0 A CMD[7:0] N P

SADDR[6:0] 0 A CMD[7:0] AANP

DATA[7:0] DATA[7:0] ... N

SADDR[6:0] 0 A CMD[7:0] A Sr ADDR[6:0] 1 A DATA[7:0] A... DATA[7:0] N P

Address

0x7F

DataFrom

addr0x7F

DataFrom

addr0x00

Not Recommended for New Designs

bq27541

SLUS861 –DECEMBER 2008

www.ti.com

I2C INTERFACE

The fuel gauge supports the standard I2C read, incremental read, one-byte write quick read, and functions. The

7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The 8-bit

device address is therefore 0xaa or 0xab for write or read, respectively.

Figure 5. Supported I2C formats: (a) 1-byte write, (b) quick read, (c) 1 byte-read, and (d) incremental read

(S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).

The quick read returns data at the address indicated by the address pointer. The address pointer, a register

internal to the I2C communication engine, increments whenever data is acknowledged by the bq27500 or the I2C

master. Quick writes function in the same manner and are a convenient means of sending multiple bytes to

consecutive command locations (such as two-byte commands that require two bytes of data).

Attempt to write a read-only address (NACK after data sent by master):

Attempt to read an address above 0x7F (NACK command):

Attempt at incremental writes (NACK all extra data bytes sent):

Incremental read at the maximum allowed read address:

The I2C engine releases both SDA and SCL if the I2C bus is held low for t(BUSERR). If the fuel gauge was holding

the lines, releasing them frees the master to drive the lines. If an external condition is holding either of the lines

low, the I2C engine enters the low-power sleep mode.

I2C Time Out

The I2C engine will release both SDA and SCL if the I2C bus is held low for about 2 seconds. If the bq27541 was

holding the lines, releasing them will free for the master to drive the lines.

Product Folder Link(s): bq27541

Not Recommended for New Designs

bq27541

www.ti.com

SLUS861 –DECEMBER 2008

REFERENCE SCHEMATIC

Product Folder Link(s): bq27541

PACKAGE OPTION ADDENDUM

www.ti.com 23-Oct-2010

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status (1) Package Type Package

Drawing Pins Package Qty Eco Plan (2) Lead/

Ball Finish MSL Peak Temp (3) Samples

(Requires Login)

BQ27541DRZR NRND SON DRZ 12 3000 Green (RoHS

& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Replaced by

BQ27541DRZR-V200

BQ27541DRZT NRND SON DRZ 12 250 Green (RoHS

& no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Replaced by

BQ27541DRZT-V200

(1) The marketing status values are defined as follows:

ACTIVE: Product device recommended for new designs.

LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.

NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.

PREVIEW: Device has been announced but is not in production. Samples may or may not be available.

OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability

information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.

Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that

lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.

Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between

the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.

Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight

in homogeneous material)

(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information

provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and

continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.

TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

BQ27541DRZR SON DRZ 12 3000 330.0 12.4 2.8 4.3 1.2 4.0 12.0 Q2

BQ27541DRZT SON DRZ 12 250 330.0 12.4 2.8 4.3 1.2 4.0 12.0 Q2

PACKAGE MATERIALS INFORMATION

www.ti.com 16-Feb-2012

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

BQ27541DRZR SON DRZ 12 3000 338.1 338.1 20.6

BQ27541DRZT SON DRZ 12 250 338.1 338.1 20.6

PACKAGE MATERIALS INFORMATION

www.ti.com 16-Feb-2012

Pack Materials-Page 2

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,

and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should

obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are

sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard

warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where

mandated by government requirements, testing of all parameters of each product is not necessarily performed.

TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and

applications using TI components. To minimize the risks associated with customer products and applications, customers should provide

adequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,

or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information

published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a

warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual

property of the third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied

by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive

business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional

restrictions.

Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all

express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not

responsible or liable for any such statements.

TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably

be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing

such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and

acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products

and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be

provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in

such safety-critical applications.

TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are

specifically designated by TI as military-grade or "enhanced plastic."Only products designated by TI as military-grade meet military

specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at

the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.

TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are

designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated

products in automotive applications, TI will not be responsible for any failure to meet such requirements.

Following are URLs where you can obtain information on other Texas Instruments products and application solutions:

Products Applications

Audio www.ti.com/audio Automotive and Transportation www.ti.com/automotive

Amplifiers amplifier.ti.com Communications and Telecom www.ti.com/communications

Data Converters dataconverter.ti.com Computers and Peripherals www.ti.com/computers

DLP®Products www.dlp.com Consumer Electronics www.ti.com/consumer-apps

DSP dsp.ti.com Energy and Lighting www.ti.com/energy

Clocks and Timers www.ti.com/clocks Industrial www.ti.com/industrial

Interface interface.ti.com Medical www.ti.com/medical

Logic logic.ti.com Security www.ti.com/security

Power Mgmt power.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense

Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video

RFID www.ti-rfid.com

OMAP Mobile Processors www.ti.com/omap

Wireless Connectivity www.ti.com/wirelessconnectivity

TI E2E Community Home Page e2e.ti.com

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265