LTC2990IMS#PBF - ANALOG DEVICES

LTC2990

Rev. F

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TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Quad I2C Voltage, Current

and Temperature Monitor

The LTC

2990 is used to monitor system temperatures,

voltages and currents. Through the I2C serial interface,

the device can be configured to measure many combi-

nations of internal temperature, remote temperature,

remote voltage, remote current and internal VCC. The

internal 10ppm/°C reference minimizes the number of

supporting components and area required. Selectable

address and configurable functionality give the LTC2990

flexibility to be incorporated in various systems needing

temperature, voltage or current data. The LTC2990 fits

well in systems needing sub-millivolt voltage resolution,

1% current measurement and 1°C temperature accuracy

or any combination of the three.

Temperature Total Unadjusted Error

n Temperature Measurement

n Supply Voltage Monitoring

n Current Measurement

n Remote Data Acquisition

n Environmental Monitoring

n Measures Voltage, Current and Temperature

n Measures Two Remote Diode Temperatures

n ±0.5°C Accuracy, 0.06°C Resolution (Typ)

n ±1°C Internal Temperature Sensor (Typ)

n 14-Bit ADC Measures Voltage/Current

n 3V to 5.5V Supply Operating Voltage

n Four Selectable Addresses

n Internal 10ppm/°C Voltage Reference

n 10-Lead MSOP Package

VCC V1

LTC2990

TINTERNAL

RSENSE

2.5V

GND

SDA

SCL

ADR0

ADR1

MEASURES: TWO SUPPLY VOLTAGES,

SUPPLY CURRENT, INTERNAL AND

REMOTE TEMPERATURES

ILOAD

TREMOTE

2990 TA01a

Voltage, Current, Temperature Monitor

All registered trademarks and trademarks are the property of their respective owners.

TAMB (°C)

–50

TUE (°C)

2990 TA01b

1.0

–25 0 50

–0.5

–1.0

0.5

75 100 125

TREMOTE

LTC2990

Rev. F

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PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS

(Note 1)

GND

VCC

ADR1

ADR0

SCL

SDA

TOP VIEW

MS PACKAGE

10-LEAD PLASTIC MSOP

JMAX

= 125°C, θ

= 150°C/W

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC2990CMS#PBF LTC2990CMS#TRPBF LTDSQ 10-Lead Plastic MSOP 0°C to 70°C

LTC2990IMS#PBF LTC2990IMS#TRPBF LTDSQ 10-Lead Plastic MSOP –40°C to 85°C

LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC2990CMS LTC2990CMS#TR LTDSQ 10-Lead Plastic MSOP 0°C to 70°C

LTC2990IMS LTC2990IMS#TR LTDSQ 10-Lead Plastic MSOP –40°C to 85°C

Consult the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

Contact the factory for parts trimmed to ideality factors other than 1.004.

Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.

Supply Voltage VCC ................................... –0.3V to 6.0V

Input Voltages V1, V2, V3, V4, SDA, SCL,

ADR1, ADR2 ..................................–0.3V to (VCC + 0.3V)

Operating Temperature Range

LTC2990C ................................................ 0°C to 70°C

LTC2990I .............................................–40°C to 85°C

Storage Temperature Range .................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec) ...................300°C

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

General

VCC Input Supply Range l2.9 5.5 V

ICC Input Supply Current During Conversion, I2C Inactive l1.1 1.8 mA

ISD Input Supply Current Shutdown Mode, I2C Inactive l1 5 µA

VCC(UVL) Input Supply Undervoltage Lockout l1.3 2.1 2.7 V

Measurement Accuracy

TINT(TUE) Internal Temperature Total Unadjusted

Error

TAMB = 0°C to 85°C

TAMB = –40°C to 0°C

±0.5

±1

±3

±3.5 °C

°C

TRMT(TUE) Remote Diode Temperature Total

Unadjusted Error η = 1.004 (Note 4) l±0.5 ±1.5 °C

VCC(TUE) VCC Voltage Total Unadjusted Error l±0.1 ±0.25 %

Vn(TUE) V1 Through V4 Total Unadjusted Error l±0.1 ±0.25 %

VDIFF(TUE) Differential Voltage Total Unadjusted Error

V1 – V2 or V3 – V4 –300mV ≤ VD ≤ 300mV l±0.2 ±0.75 %

VDIFF(MAX) Maximum Differential Voltage l–300 300 mV

LTC2990

Rev. F

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ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VOFFSET_DIFF Differential Offset V1 = V2 = VCC, V3 = V4 = 0V –12.5 0 12.5 LSB

VOFFSET_SE Single-Ended Offset V1, V2, V3, V4 = 0V –6 0 6 LSB

VDIFF(CMR) Differential Voltage Common Mode Range l0 VCC V

VLSB(DIFF) Differential Voltage LSB Weight 19.42 µV

VLSB(SINGLE-ENDED) Single-Ended Voltage LSB Weight 305.18 µV

VLSB(TEMP) Temperature LSB Weight Celsius or Kelvin 0.0625 Deg

TNOISE Temperature Noise Celsius or Kelvin

TMEAS = 46ms (Note 2) 0.2

0.05 °RMS

°/√Hz

Res Resolution (No Missing Codes) (Note 2) l14 Bits

INL Integral Nonlinearity 2.9V ≤ VCC ≤ 5.5V, VIN(CM) = 1.5V

(Note 2)

Single-Ended

Differential

–2

LSB

CIN V1 Through V4 Input Sampling

Capacitance (Note 2) 0.35 pF

IIN(AVG) V1 Through V4 Input Average Sampling

Current 0V ≤ VN ≤ 3V (Note 2) 0.6 µA

IDC_LEAK(VIN) V1 Through V4 Input Leakage Current 0V ≤ VN ≤ VCC l–10 10 nA

Measurement Delay

TINT

, TR1, TR2 Per Configured Temperature Measurement (Note 2) l37 46 55 ms

V1, V2, V3, V4 Single-Ended Voltage Measurement (Note 2) Per Voltage, Two Minimum l1.2 1.5 1.8 ms

V1 – V2, V3 – V4 Differential Voltage Measurement (Note 2) l1.2 1.5 1.8 ms

VCC VCC Measurement (Note 2) l1.2 1.5 1.8 ms

Max Delay Mode[4:0] = 11101, TINT

, TR1, TR2, VCC (Note 2) l167 ms

V1, V3 Output (Remote Diode Mode Only)

IOUT Output Current Remote Diode Mode l260 350 µA

VOUT Output Voltage l0 VCC V

I2C Interface

VADR(L) ADR0, ADR1 Input Low Threshold Voltage Falling l0.3 • VCC V

VADR(H) ADR0, ADR1 Input High Threshold Voltage Rising l0.7 • VCC V

VOL1 SDA Low Level Maximum Voltage IO = –3mA, VCC = 2.9V to 5.5V l0.4 V

VIL Maximum Low Level Input Voltage SDA and SCL Pins l0.3 • VCC V

VIH Minimum High Level Input Voltage SDA and SCL Pins l0.7 • VCC V

ISDAI,SCLI SDA, SCL Input Current 0 < VSDA,SCL < VCC l±1 µA

IADR(MAX) Maximum ADR0, ADR1 Input Current ADR0 or ADR1 Tied to VCC or GND l±1 µA

I2C Timing (Note 2)

fSCL(MAX) Maximum SCL Clock Frequency 400 kHz

tLOW Minimum SCL Low Period 1.3 µs

tHIGH Minimum SCL High Period 600 ns

tBUF(MIN) Minimum Bus Free Time Between Stop/

Start Condition 1.3 µs

tHD,STA(MIN) Minimum Hold Time After (Repeated)

Start Condition 600 ns

LTC2990

Rev. F

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Note 1: Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2: Guaranteed by design and not subject to test.

Note 3: Integral nonlinearity is defined as the deviation of a code from a

straight line passing through the actual endpoints of the transfer curve.

The deviation is measured from the center of the quantization band.

Note 4: Trimmed to an ideality factor of 1.004 at 25°C. Remote diode

temperature drift (TUE) verified at diode voltages corresponding to

the temperature extremes with the LTC2990 at 25°C. Remote diode

temperature drift (TUE) guaranteed by characterization over the LTC2990

operating temperature range.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

tSU,STA(MIN) Minimum Repeated Start Condition Set-Up

Time 600 ns

tSU,STO(MIN) Minimum Stop Condition Set-Up Time 600 ns

tHD,DATI(MIN) Minimum Data Hold Time Input 0 ns

tHD,DATO(MIN) Minimum Data Hold Time Output 300 900 ns

tSU,DAT(MIN) Minimum Data Set-Up Time Input 100 ns

tSP(MAX) Maximum Suppressed Spike Pulse Width 50 250 ns

CXSCL, SDA Input Capacitance 10 pF

The l denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted.

ELECTRICAL CHARACTERISTICS

LTC2990

Rev. F

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TYPICAL PERFORMANCE CHARACTERISTICS

TINTERNAL Error

Remote Diode Error with LTC2990

at 25°C, 90°C

Remote Diode Error with LTC2990

at Same Temperature as Diode

Supply Current vs Temperature

Shutdown Current vs Temperature

Measurement Delay Variation

vs T Normalized to 3.3V, 25°C

VCC TUE Single-Ended VX TUE Differential Voltage TUE

TA = 25°C, VCC = 3.3V unless otherwise noted

TAMB (°C)

–50

ICC (µA)

2.0

2.5

3.0

25 50 75 100 125

2990 G01

1.5

1.0

–25 0 150

0.5

3.5

VCC = 5V

VCC = 3.3V

TAMB (°C)

–50

ICC (µA)

1050

1100

1150

25 50 75 100 125

2990 G02

–25 0 150

1000

950

1200

VCC = 5V

VCC = 3.3V

TAMB (°C)

–50

MEASUREMENT DELAY VARIATION (%)

25 50 75 100 125

2990 G03

–25 0 150

–1

VCC = 5V

VCC = 3.3V

TAMB (°C)

–50

VCC TUE (%)

0.05

25 50 75 100 125

2990 G04

–25 0 150

–0.05

–0.10

0.10

TAMB (°C)

–50

VX TUE (%)

0.05

25 50 75 100 125

2990 G05

–25 0 150

–0.05

–0.10

0.10

TAMB (°C)

–50

VDIFF TUE (%)

0.5

25 50 75 100 125

2990 G06

–25 0 150

–0.5

–1.0

1.0

VCC = 5V

VCC = 3.3V

BATH TEMPERATURE (°C)

–50

LTC2990 TRX ERROR (°C)

0.2

0.4

25 50 75 100 125

2990 G08

–0.2

–25 0 150

–0.4

–0.6

0.6

LTC2990

AT 25°C

LTC2990

AT 90°C

TAMB (°C)

–50

TINTERNAL ERROR (DEG)

25 50 75 100 125

2990 G07

–1

–25 0 150

–2

–3

TAMB (°C)

–50

LTC2990 TRX ERROR (DEG)

0.25

0.50

0.75

25 50 75 100 125

2990 G09

–0.25

–25 0 150

–0.50

–1.00

–0.75

1.00

LTC2990

Rev. F

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Single-Ended Noise Single-Ended Transfer Function Single-Ended INL

LTC2990 Differential Noise Differential Transfer Function Differential INL

TYPICAL PERFORMANCE CHARACTERISTICS

TA = 25°C, VCC = 3.3V unless otherwise noted

LSBs (305.18µV/LSB)

–3

COUNTS

3500

2990 G10

2000

1000

–2 –1 1

500

4000

4800 READINGS

3000

2500

1500

2 3

VX (V)

–1

2 4

2990 G11

–0 1 3 5 6

–1

LTC2990 VALUE (V)

VCC = 5V

VCC = 3.3V

LSBs (19.42µV/LSB)

–4

COUNTS

300

400

500

800 READINGS

–1 1

2990 G13

200

100

0–3 –2 02 3

V1-V2 (V)

–0.4

LTC2990 V1-V2 (V)

0.2

0.4

2990 G14

–0.2

–0.4 –0.2 00.2

–0.3 –0.1 0.1 0.3

0.4

–0.1

0.1

–0.3

0.3

TINT Noise Remote Diode Noise POR Thresholds vs Temperature

(°C)

–0.75 –0.5

COUNTS

200

500

1000 READINGS

–0.25 0.25 0.5

2990 G16

100

400

300

00.75

(°C)

–0.75 –0.5

COUNTS

200

600

1000 READINGS

500

–0.25 0.25 0.5

2990 G17

100

400

300

00.75

TAMB (°C)

–50

THRESHOLD (V)

1.8

2.2

150

2990 G18

1.4

1.0 050 100

–25 25 75 125

2.6

1.6

2.0

1.2

2.4 VCC RISING

VCC FALLING

VX (V)

–1.0

INL (LSBs)

–0.5

0.5

1.0

1234

2990 G12

VCC = 5V

VCC = 3.3V

VIN (V)

–0.4

INL (LSBs)

0.4

2990 G15

–1

–2 –0.2 00.2

LTC2990

Rev. F

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PIN FUNCTIONS

V1 (Pin 1): First Monitor Input. This pin can be config-

ured as a single-ended input or the positive input for a

differential or remote diode temperature measurement (in

combination with V2). When configured for remote diode

temperature, this pin will source a current.

V2 (Pin 2): Second Monitor Input. This pin can be con-

figured as a single-ended input or the negative input for a

differential or remote diode temperature measurement (in

combination with V1). When configured for remote diode

temperature, this pin will have an internal termination,

while the measurement is active.

V3 (Pin 3): Third Monitor Input. This pin can be config-

ured as a single-ended input or the positive input for a

differential or remote diode temperature measurement (in

combination with V4). When configured for remote diode

temperature, this pin will source a current.

V4 (Pin 4): Fourth Monitor Input. This pin can be config-

ured as a single-ended input or the negative input for a

differential or remote diode temperature measurement (in

combination with V3). When configured for remote diode

temperature, this pin will have an internal termination,

while the measurement is active.

GND (Pin 5): Device Circuit Ground. Connect this pin to a

ground plane through a low impedance connection.

SDA (Pin 6): Serial Bus Data Input and Output. In the

transmitter mode (Read), the conversion result is output

through the SDA pin, while in the receiver mode (Write),

the device configuration bits are input through the SDA

pin. At data input mode, the pin is high impedance; while

at data output mode, it is an open-drain N-channel driver

and therefore an external pull-up resistor or current

source to VCC is needed.

SCL (Pin 7): Serial Bus Clock Input. The LTC2990 can

only act as a slave and the SCL pin only accepts exter-

nal serial clock. The LTC2990 does not implement clock

stretching.

ADR0 (Pin 8): Serial Bus Address Control Input. The

ADR0 pin is an address control bit for the device I2C

address. See Table2.

ADR1 (Pin 9): Serial Bus Address Control Input. The

ADR1 pin is an address control bit for the device I2C

address. See Table2.

VCC (Pin 10): Supply Voltage Input.

LTC2990

Rev. F

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FUNCTIONAL DIAGRAM

ADC

MUX

MODE

REFERENCE

I2C

UNDERVOLTAGE

DETECTOR

VCC

INTERNAL

SENSOR

REMOTE

DIODE

SENSORS

ADR1

2990 FD

CONTROL

LOGIC

ADR0 8

SDA 6

SCL 7

GND 5

VCC 10

TIMING DIAGRAM

tSU, DAT tSU, STO

tSU, STA tBUF

tHD, STA

tSP

tHD, DATO,

tHD, DATI

tHD, STA

START

CONDITION

STOP

CONDITION

REPEATED START

CONDITION

START

CONDITION

2990 TD

SDA

SCL

LTC2990

Rev. F

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OPERATION

The LTC2990 monitors voltage, current, internal and

remote temperatures. It can be configured through an

I2C interface to measure many combinations of these

parameters. Single or repeated measurements are pos-

sible. Remote temperature measurements use a transistor

as a temperature sensor, allowing the remote sensor to

be a discrete NPN (ex. MMBT3904) or an embedded PNP

device in a microprocessor or FPGA. The internal ADC

reference minimizes the number of support components

required.

The Functional Diagram displays the main components of

the device. The input signals are selected with an input

MUX, controlled by the control logic block. The control

logic uses the mode bits in the control register to manage

the sequence and types of data acquisition. The control

logic also controls the variable current sources during

remote temperature acquisition. The order of acquisitions

is fixed: TINTERNAL, V1, V2, V3, V4 then VCC. The ADC

performs the necessary conversion(s) and supplies the

data to the control logic for further processing in the case

of temperature measurements, or routing to the appropri-

ate data register for voltage and current measurements.

Current and temperature measurements, V1 – V2 or V3

– V4, are sampled differentially by the internal ADC. The

I2C interface supplies access to control, status and data

registers. The ADR1 and ADR0 pins select one of four

possible I2C addresses (see Table2). The undervoltage

detector inhibits I2C communication below the specified

threshold. During an undervoltage condition, the part is in

a reset state, and the data and control registers are placed

in the default state of 00h.

Remote diode measurements are conducted using mul-

tiple ADC conversions and source currents to compen-

sate for sensor series resistance. During temperature

measurements, the V2 or V4 terminal of the LTC2990

is terminated with a diode. The LTC2990 is calibrated to

yield the correct temperature for a remote diode with an

ideality factor of 1.004. See the applications section for

compensation of sensor ideality factors other than the

factory calibrated value of 1.004.

The LTC2990 communicates through an I2C serial inter-

face. The serial interface provides access to control, sta-

tus and data registers. I

C defines a 2-wire open-drain

interface supporting multiple slave devices and masters

on a single bus. The LTC2990 supports 100kbits/s in the

standard mode and up to 400kbit/s in fast mode. The

four physical addresses supported are listed in Table2.

The I2C interface is used to trigger single conversions, or

start repeated conversions by writing to a dedicated trig-

ger register. The data registers contain a destructive-read

status bit (data valid), which is used in repeated mode to

determine if the register ’s contents have been previously

read. This bit is set when the register is updated with new

data, and cleared when read.

VCC V1

LTC2990

2.5V

2-WIRE

I2C

INTERFACE

GND

SDA

SCL

ADR0

ADR1

470pF

MMBT3904

RSENSE

15mΩ

ILOAD

2990 F01

0.1µF

Figure1 is the basic LTC2990 application circuit.

Figure1.

APPLICATIONS INFORMATION

Power Up

The VCC pin must exceed the undervoltage (UV) thresh-

old of 2.5V to keep the LTC2990 out of power-on reset.

Power-on reset will clear all of the data registers and the

control register.

Temperature Measurements

The LTC2990 can measure internal temperature and up

to two external diode or transistor sensors. During tem-

perature conversion, current is sourced through either the

V1 or the V3 pin to forward bias the sensing diode. The

LTC2990

Rev. F

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APPLICATIONS INFORMATION

Figure2. Recommended PCB Layout

VCC

ADR1

ADR0

SCL

SDA

LTC2990

2990 F02

GND SHIELD

TRACE

NPN SENSOR

470pF

0.1µF

GND

change in sensor voltage per degree temperature change

is 275µV/°C, so environmental noise must be kept to a

minimum. Recommended shielding and PCB trace con-

siderations are illustrated in Figure2.

The diode equation:

VBE = η• k • T

q•ln IC

⎛

⎝

⎜⎞

⎠

⎟

(1)

can be solved for T, where T is Kelvin degrees, I

is a

process dependent factor on the order of 1E-13, η is the

diode ideality factor, k is Boltzmann’s constant and q is

the electron charge.

T=VBE •q

η•k•In IC

⎛

⎝

⎜⎞

⎠

⎟

(2)

The LTC2990 makes differential measurements of diode

voltage to calculate temperature. Proprietary techniques

allow for cancellation of error due to series resistance.

ideality factor of the diode sensor can be considered a

temperature scaling factor. The temperature error for a

1% accurate ideality factor error is 1% of the Kelvin tem-

perature. Thus, at 25°C, or 298K, a +1% accurate ideality

factor error yields a +2.98 degree error. At 85°C or 358K, a

+1% error yields a 3.6 degree error. It is possible to scale

the measured Kelvin or Celsius temperature measured

using the LTC2990 with a sensor ideality factor other than

1.004, to the correct value. The scaling Equations (3) and

(4) are simple, and can be implemented with sufficient

precision using 16-bit fixed-point math in a microproces-

sor or microcontroller.

Factory Ideality Calibration Value:

ηCAL = 1.004

Actual Sensor Ideality Value:

ηACT

Compensated Kelvin Temperature:

TK _ COMP =ηCAL

ACT

• TK _MEAS

(3)

Compensated Celsius Temperature

TC _ COMP =ηCAL

ηACT

•TC _MEAS +273

( )

⎡

⎣

⎢

⎤

⎦

⎥– 273

(4)

A 16-bit unsigned number is capable of representing the

ratio ηCAL/ηACT in a range of 0.00003 to 1.99997, by

multiplying the fractional ratio by 215. The range of scal-

ing encompasses every conceivable target sensor value.

The ideality factor scaling granularity yields a worst-case

Ideality Factor Scaling

The LTC2990 is factory calibrated for an ideality factor of

1.004, which is typical of the popular MMBT3904 NPN

transistor. The semiconductor purity and wafer-level pro-

cessing limits device-to-device variation, making these

devices interchangeable (typically <0.5°C) for no addi-

tional cost. Several manufacturers supply suitable transis-

tors, some recommended sources are listed in Table1.

Discrete 2-terminal diodes are not recommended as tem-

perature sensors. While an ideality factor value of 1.004

is typical of target sensors, small deviations can yield

significant temperature errors. Contact LTC Marketing for

parts trimmed to ideality factors other than 1.004. The

Table1. Recommended Transistors to Be Used as Temperature

Sensors

MANUFACTURER PART NUMBER PACKAGE

Fairchild Semiconductor MMBT3904

FMMT3904 SOT-23

SOT-23

Central Semiconductor CMPT3904

CET3904E SOT-23

SOT-883L

Diodes, Inc. MMBT3904 SOT-23

On Semiconductor MMBT3904LT1 SOT-23

NXP MMBT3904 SOT-23

Infineon MMBT3904 SOT-23

Rohm UMT3904 SC-70

LTC2990

Rev. F

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APPLICATIONS INFORMATION

temperature error of 0.01° at 125°C. Multiplying this

16-bit unsigned number and the measured Kelvin

(unsigned) temperature represented as a 16-bit number,

yields a 32-bit unsigned result. To scale this number back

to a 13-bit temperature (9-bit integer part, and a 4-bit

fractional part), divide the number by 2

per Equation (5).

Similarly, Celsius coded temperature values can be scaled

using 16-bit fixed-point arithmetic, using Equation (6).

In both cases, the scaled result will have a 9-bit integer

(d[12:4]) and the 4LSBs (d[3:0]) representing the 4-bit

fractional part. To convert the corrected result to decimal,

divide the final result by 24 or 16, as you would the reg-

ister contents. If ideality factor scaling is implemented

in the target application, it is beneficial to configure the

LTC2990 for Kelvin coded results to limit the number of

math operations required in the target processor.

TK _COMP =

Unsigned

( )

ηCAL

ηACT

215

⎛

⎝

⎜⎞

⎠

⎟TK _MEAS

(5)

TC _ COMP =

Unsigned

( )

ηCAL

ηACT

215

⎛

⎝

⎜⎞

⎠

⎟TC _ MEAS +273.15 • 24

( )

215

– 273.15 • 2

(6)

Sampling Currents

Single-ended voltage measurements are directly sampled

by the internal ADC. The average ADC input current is a

function of the input applied voltage as follows:

IIN(AVG) = (VIN – 1.49V) • 0.17[µA/V]

Inputs with source resistance less than 200Ω will yield

full-scale gain errors due to source impedance of <1/2LSB

for 14-bit conversions. The nominal conversion time is

1.5ms for single-ended conversions.

Current Measurements

The LTC2990 has the ability to perform 14-bit current

measurements with the addition of a current sense resis-

tor (see Figure3).

In order to achieve accurate current sensing a few details

must be considered. Differential voltage or current

measurements are directly sampled by the internal ADC.

The average ADC input current for each leg of the differ-

ential input signal during a conversion is (VIN – 1.49V)

• 0.34[µA/V]. The maximum source impedance to yield

14-bit results with, 1/2LSB full-scale error is ~50Ω. In

order to achieve high accuracy 4-point, or Kelvin con

nected measurements of the sense resistor differential

voltage are necessary.

In the case of current measurements, the external sense

resistor is typically small, and determined by the full-

scale input voltage of the LTC2990. The full-scale dif-

ferential voltage is 0.300V. The external sense resistance

is then a function of the maximum measurable current,

or REXT_MAX = 0.300V/IMAX. For example, if you wanted

to measure a current range of ±5A, the external shunt

resistance would equal 0.300V/5A = 60mΩ.

There exists a way to improve the sense resistor’s preci-

sion using the LTC2990. The LTC2990 measures both dif-

ferential voltage and remote temperature. It is therefore,

possible to compensate for the absolute resistance toler-

ance of the sense resistor and the temperature coefficient

of the sense resistor in software. The resistance would be

measured by running a calibrated test current through the

discrete resistor. The LTC2990 would measure both the

differential voltage across this resistor and the resistor

temperature. From this measurement, RO and TO in the

equation below would be known. Using the two equations,

the host microprocessor could compensate for both the

absolute tolerance and the TCR.

RT = RO • [1 + α(T – TO)]

where:

α = +3930 ppm/°C for copper trace

α = ±2 to ~+200ppm/°C for discrete R (7)

I = (V1 – V2)/RT (8)

Figure3. Simplified Current Sense Schematic

V1 V2

LTC2990

0V – VCC

RSENSE

ILOAD

2990 F03

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

Device Configuration

The LTC2990 is configured by writing the control register

through the serial interface. Refer to Table5 for control reg-

ister bit definition. The device is capable of many applica-

tion configurations including voltage, temperature and cur-

rent measurements. It is possible to configure the device

for single or repeated acquisitions. The device can make

single measurements, or in continuous mode, repeated

acquisitions. When the device is configured for multiple

measurements, the order of the measurements is fixed.

For repeated acquisitions, only an initial trigger is required

after which data registers are continuously refreshed with

new data. As each new data result is ready, the MSB of the

corresponding data register is set, and the corresponding

status register bit is set. These bits are cleared when the

corresponding data register is addressed. The configura-

tion register value at power-up causes the part to measure

only the internal temperature sensor when triggered. The

four input pins V1 through V4 will be in a high impedance

state, until configured otherwise, and a measurement is

triggered. The data registers are double-buffered in order

to ensure upper and lower data bytes do not become out

of sync. Read operations must be terminated in order to

avoid an indefinitely paused wait state. Reading the STATUS

polling system, it is recommended that the STATUS register

be tested for new data, this prevents unnecessary delays

updating the measurement registers.

Data Format

The data registers are broken into 8-bit upper and lower

bytes. Voltage and current conversions are 14-bits. The

upper bits in the MSB registers provide status on the

resulting conversions. These status bits are different for

temperature and voltage conversions:

Temperature: Temperature conversions are reported as

Celsius or Kelvin results described in Table8 and Table9,

each with 0.0625 degree-weighted LSBs. The format is

controlled by the control register, Bit 7. All temperature

formats, TINT

, TR1 and TR2 are controlled by this bit. The

Temperature MSB result register most significant bit

(Bit 7) is the DATA_VALID bit, which indicates whether

the current register contents have been accessed since

the result was written to the register. This bit will be set

when new data is written to the register, and cleared when

accessed. Bit 6 of the register is a sensor-shorted alarm.

This bit of the corresponding register will be high if the

remote sensor diode differential voltage is below 0.14V.

The LTC2990 internal bias circuitry maintains this voltage

above this level during normal operating conditions. Bit

5 of the register is a sensor open alarm. This bit of the

corresponding register will be high if the remote sensor

diode differential voltage is above 1.0VDC. The LTC2990

internal bias circuitry maintains this voltage below this

level during normal operating conditions. The two sensor

alarms are only valid after a completed conversion indi-

cated by the data_valid bit being high. Bit 4 through Bit 0

of the MSB register are the conversion result bits D[12:8],

in two’s compliment format. Note in Kelvin results, the

result will always be positive. The LSB register contains

temperature result bits D[7:0]. To convert the register

contents to temperature, use the following equation:

T = D[12:0]/16.

See Table10 for conversion value examples.

Voltage/Current: Voltage results are reported in two

respective registers, an MSB and LSB register. The

Voltage MSB result register most significant bit (Bit 7)

is the data_valid bit, which indicates whether the current

written to the register. This bit will be set when the register

contents are new, and cleared when accessed. Bit 6 of the

MSB register is the sign bit, Bits 5 though 0 represent

bits D[13:8] of the two’s complement conversion result.

The LSB register holds conversion bits D[7:0]. The LSB

value is different for single-ended voltage measurements

V1 through V4, and differential (current measurements)

V1 – V2 and V3 – V4. Single-ended voltages are limited

to positive values in the range 0V to 3.5V. Differential

voltages can have input values in the range of –0.300V

to 0.300V.

Use the following equations to convert the register values

(see Table10 for examples):

VSINGLE-ENDED = D[14:0] • 305.18µV, if Sign = 0

VSINGLE-ENDED = (D[14:0] +1) • –305.18µV, if Sign = 1

VDIFFERENTIAL = D[14:0] • 19.42µV, if Sign = 0

DIFFERENTIAL

= (D[14:0] +1) • –19.42µV, if Sign = 1

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

Current = D[14:0] • 19.42µV/RSENSE, if Sign = 0

Current = (D[14:0] +1) • –19.42µV/RSENSE, if Sign = 1

where RSENSE is the current sensing resistor, typically

<1Ω.

: The LTC2990 measures V

. To convert the contents

of the VCC register to voltage, use the following equation:

VCC = 2.5 + D[13:0] • 305.18µV

Digital Interface

The LTC2990 communicates with a bus master using a

two-wire interface compatible with the I2C Bus and the

SMBus, an I2C extension for low power devices.

The LTC2990 is a read-write slave device and supports

SMBus bus Read Byte Data and Write Byte Data, Read Word

Data and Write Word Data commands. The data formats for

these commands are shown in Table3 throughTable10.

The connected devices can only pull the bus wires LOW

and can never drive the bus HIGH. The bus wires are

externally connected to a positive supply voltage via a cur-

rent source or pull-up resistor. When the bus is free, both

lines are HIGH. Data on the I2C bus can be transferred at

rates of up to 100kbit/s in the standard mode and up to

400kbit/s in the fast mode. Each device on the I2C bus is

recognized by a unique address stored in that device and

can operate as either a transmitter or receiver, depending

on the function of the device. In addition to transmitters

and receivers, devices can also be considered as masters

or slaves when performing data transfers. A master is

the device which initiates a data transfer on the bus and

generates the clock signals to permit that transfer. At the

same time any device addressed is considered a slave.

The LTC2990 can only be addressed as a slave. Once

addressed, it can receive configuration bits or transmit

the last conversion result. Therefore the serial clock line

SCL is an input only and the data line SDA is bidirec-

tional. The device supports the standard mode and the

fast mode for data transfer speeds up to 400kbit/s. The

Timing Diagram shows the definition of timing for fast/

standard mode devices on the I2C bus. The internal state

machine cannot update internal data registers during an

C read operation. The state machine pauses until the I

read is complete. It is therefore, important not to leave

the LTC2990 in this state for long durations, or increased

conversion latency will be experienced.

START and STOP Conditions

When the bus is idle, both SCL and SDA must be high. A

bus master signals the beginning of a transmission with

a START condition by transitioning SDA from high to low

while SCL is high. When the bus is in use, it stays busy

if a repeated START (SR) is generated instead of a STOP

condition. The repeated START (SR) conditions are func-

tionally identical to the START (S). When the master has

finished communicating with the slave, it issues a STOP

condition by transitioning SDA from low to high while SCL

is high. The bus is then free for another transmission.

I2C Device Addressing

Four distinct bus addresses are configurable using the

ADR0-ADR1 pins. There is also one global sync address

available at EEh which provides an easy way to synchro-

nize multiple LTC2990s on the same I2C bus. This allows

write only access to all 2990s on the bus for simultaneous

triggering. Table2 shows the correspondence between

ADR0 and ADR1 pin states and addresses.

Acknowledge

The acknowledge signal is used for handshaking between

the transmitter and the receiver to indicate that the last

byte of data was received. The transmitter always releases

the SDA line during the acknowledge clock pulse. When

the slave is the receiver, it must pull down the SDA line

so that it remains LOW during this pulse to acknowledge

receipt of the data. If the slave fails to acknowledge by

leaving SDA HIGH, then the master can abort the transmis-

sion by generating a STOP condition. When the master is

receiving data from the slave, the master must pull down

the SDA line during the clock pulse to indicate receipt of

the data. After the last byte has been received the master

will leave the SDA line HIGH (not acknowledge) and issue

a STOP condition to terminate the transmission.

Write Protocol

The master begins communication with a START condi-

tion followed by the seven bit slave address and the R/W#

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

bit set to zero. The addressed LTC2990 acknowledges

the address and then the master sends a command byte

which indicates which internal register the master wishes

to write. The LTC2990 acknowledges the command byte

and then latches the lower four bits of the command byte

into its internal Register Address pointer. The master then

delivers the data byte and the LTC2990 acknowledges

once more and latches the data into its internal register.

The transmission is ended when the master sends a STOP

condition. If the master continues sending a second data

byte, as in a Write Word command, the second data byte

will be acknowledged by the LTC2990 and written to the

next register in sequence, if this register has write access.

Read Protocol

The master begins a read operation with a START condi-

tion followed by the seven bit slave address and the R/W#

bit set to zero. The addressed LTC2990 acknowledges

this and then the master sends a command byte which

indicates which internal register the master wishes to

read. The LTC2990 acknowledges this and then latches

the lower four bits of the command byte into its inter-

nal Register Address pointer. The master then sends a

repeated START condition followed by the same seven bit

address with the R/W# bit now set to one. The LTC2990

acknowledges and sends the contents of the requested

sends a STOP condition. The register pointer is automati-

cally incremented after each byte is read. If the master

acknowledges the transmitted data byte, as in a Read

Word command, the LTC2990 will send the contents

of the next sequential register as the second data byte.

The byte following register 0x0F is register 0x00, or the

statusregister.

Control Register

The control register (Table5) determines the selected

measurement mode of the device. The LTC2990 can be

configured to measure voltages, currents and tempera-

tures. These measurements can be single-shot or repeated

measurements. Temperatures can be set to report in

Celsius or Kelvin temperature scales. The LTC2990 can

be configured to run particular measurements, or all pos-

sible measurements per the configuration specified by the

mode bits. The power-on default configuration of the con-

trol register is set to 0x00, which translates to a repeated

measurement of the internal temperature sensor, when

triggered. This mode prevents the application of remote

diode test currents on pins V1 and V3, and remote diode

terminations on pins V2 and V4 at power-up.

Status Register

The status register (Table4) reports the status of a par-

ticular conversion result. When new data is written into a

particular result register, the corresponding DATA_VALID

bit is set. When the register is addressed by the I2C inter-

face, the status bit (as well as the DATA_VALID bit in the

respective register) is cleared. The host can then deter-

mine if the current available register data is new or stale.

The busy bit, when high, indicates a single-shot conver-

sion is in progress. The busy bit is always high during

repeated mode, after the initial conversion is triggered.

STOP

2990 F04

START ADDRESS R/W

981-71-71-7

a6-a0 b7-b0 b7-b0

9898

DATA DATAACK ACK ACK

Figure4. Data Transfer Over I2C or SMBus

S A A DATAW#ADDRESS COMMAND A

0 0 b7:b0010011a1:a0

FROM MASTER TO SLAVE

XXXXXb3:b0 0

2990 F05

FROM SLAVE TO MASTER

A: ACKNOWLEDGE (LOW)

A#: NOT ACKNOWLEDGE (HIGH)

R: READ BIT (HIGH)

W#: WRITE BIT (LOW)

S: START CONDITION

P: STOP CONDITION

Figure5. LTC2990 Serial Bus Write Byte Protocol

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

S A A SW#ADDRESS COMMAND A

0 0 1 0

DATA

b7:b0010011a1:a0

ADDRESS

10011a1:a0XXXXXb3:b0 1

2990 F07

PA#R

Figure7. LTC2990 Serial Bus Read Byte Protocol

S A A SW#ADDRESS COMMAND A

0 0 1 0

DATA

b7:b0010011a1:a0

ADDRESS

10011a1:a0XXXXXb3:b0 1

2990 F08

PA#DATA

b7:b0

Table2. I2C Base Address

HEX I2C BASE ADDRESS BINARY I2C BASE ADDRESS ADR1 ADR0

98h 1001 100X* 0 0

9Ah 1001 101X* 0 1

9Ch 1001 110X* 1 0

9Eh 1001 111X* 1 1

EEh 1110 1110 Global Sync Address

*X = R/W Bit

S A A DATAW#ADDRESS COMMAND A

0 0 b7:b0

DATA

b7:b0010011a1:a0 XXXXXb3:b0 0 0

2990 F06

Figure6. LTC2990 Serial Bus Repeated Write Byte Protocol

Figure8. LTC2990 Serial Bus Repeated Read Byte Protocol

Table3. LTC2990 Register Address and Contents

00h STATUS R Indicates BUSY State, Conversion Status

01h CONTROL R/W Controls Mode, Single/Repeat, Celsius/Kelvin

02h TRIGGER** R/W Triggers an Conversion

03h N/A Unused Address

04h TINT (MSB) R Internal Temperature MSB

05h TINT (LSB) R Internal Temperature LSB

06h V1 (MSB) R V1, V1 – V2 or TR1 MSB

07h V1 (LSB) R V1, V1 – V2 or TR1 LSB

08h V2 (MSB) R V2, V1 – V2 or TR1 MSB

09h V2 (LSB) R V2, V1 – V2 or TR1 LSB

0Ah V3 (MSB) R V3, V3 – V4 or TR2 MSB

0Bh V3 (LSB) R V3, V3 – V4 or TR2 LSB

0Ch V4 (MSB) R V4, V3 – V4 or TR2 MSB

0Dh V4 (LSB) R V4, V3 – V4 or TR2 LSB

0Eh VCC (MSB) R VCC MSB

0Fh VCC (LSB) R VCC LSB

*Register Address MSBs b7-b4 are ignored.

**Writing any value triggers a conversion. Data Returned reading this register address is the Status register.

†Power-on reset sets all registers to 00h.

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

Table4. STATUS Register (Default 0x00)

BIT NAME OPERATION

b7 0 Always Zero

b6 VCC Ready 1 = VCC Register Contains New Data, 0 = VCC Register Read

b5 V4 Ready 1 = V4 Register Contains New Data, 0 = V4 Register Read

b4 V3, TR2, V3 – V4 Ready 1 = V3 Register Contains New Data, 0 = V3 Register Data Old

b3 V2 Ready 1 = V2 Register Contains New Data, 0 = V2 Register Data Old

b2 V1, TR1, V1 – V2 Ready 1 = V1 Register Contains New Data, 0 = V1 Register Data Old

b1 TINT Ready 1 = TINT Register Contains New Data, 0 = TINT Register Data Old

b0 Busy* 1= Conversion In Process, 0 = Acquisition Cycle Complete

*In Repeat mode, Busy = 1 always

Table5. CONTROL Register (Default 0x00)

BIT NAME OPERATION

b7 Temperature Format Temperature Reported In; Celsius = 0 (Default), Kelvin = 1

b6 Repeat/Single Repeated Acquisition = 0 (Default), Single Acquisition = 1

b5 Reserved Reserved

b[4:3] Mode [4:3] Mode Description

0 0 Internal Temperature Only (Default)

0 1 TR1, V1 or V1 – V2 Only per Mode [2:0]

1 0 TR2, V3 or V3 – V4 Only per Mode [2:0]

1 1 All Measurements per Mode [2:0]

b[2:0] Mode [2:0] Mode Description

0 0 0 V1, V2, TR2 (Default)

0 0 1 V1 – V2, TR2

0 1 0 V1 – V2, V3, V4

0 1 1 TR1, V3, V4

1 0 0 TR1, V3 – V4

1 0 1 TR1, TR2

1 1 0 V1 – V2, V3 – V4

1 1 1 V1, V2, V3, V4

LTC2990

Rev. F

For more information www.analog.com

APPLICATIONS INFORMATION

Table8. Temperature Measurement MSB Data Register Format

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

DV* SS** SO†D12 D11 D10 D9 D8

*DATA_VALID is set when a new result is written into the register.

DATA_VALID is cleared when this register is addressed (read) by the I2C

interface.

**Sensor Short is high if the voltage measured on V1 is too low

during temperature measurements. This signal is always low for TINT

measurements.

†Sensor Open is high if the voltage measured on V1 is excessive

during temperature measurements. This signal is always low for TINT

measurements.

Table9. Temperature Measurement LSB Data Register Format

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

D7 D6 D5 D4 D3 D2 D1 D0

Table6. Voltage/Current Measurement MSB Data Register

Format

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

DV* Sign D13 D12 D11 D10 D9 D8

*Data Valid is set when a new result is written into the register. Data Valid

is cleared when this register is addressed (read) by the I2C interface.

Table7. Voltage/Current Measurement LSB Data Register

Format

BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0

D7 D6 D5 D4 D3 D2 D1 D0

LTC2990

Rev. F

For more information www.analog.com

Table10. Conversion Formats

VOLTAGE FORMATS SIGN BINARY VALUE D[13:0] VOLTAGE

Single-Ended

LSB = 305.18µV

0 11111111111111 >5

0 10110011001101 3.500

0 01111111111111 2.500

0 00000000000000 0.000

1 11110000101001 –0.300

Differential

LSB = 19.42µV

0 11111111111111 >0.318

0 11110001011000 +0.300

0 10000000000000 +0.159

0 00000000000000 0.000

1 10000000000000 –0.159

1 00001110101000 –0.300

1 00000000000000 <–0.318

VCC = Result + 2.5V

LSB = 305.18µV

0 10110011001101 VCC = 6V

0 10000000000000 VCC = 5V

0 00001010001111 VCC = 2.7V

TEMPERATURE FORMATS FORMAT BINARY VALUE D[12:0] TEMPERATURE

Temperature Internal, TR1 or TR2

LSB = 0.0625 Degrees

Celsius 0011111010000 +125.0000

Celsius 0000110010001 +25.0625

Celsius 0000110010000 +25.0000

Celsius 1110110000000 –40.0000

Kelvin 1100011100010 398.1250

Kelvin 1000100010010 273.1250

Kelvin 0111010010010 233.1250

APPLICATIONS INFORMATION

LTC2990

Rev. F

For more information www.analog.com

TYPICAL APPLICATIONS

High Voltage/Current and Temperature Monitoring

–

–INS 0.1µF

VIN

5V TO 105V

0.1µF

470pF

ALL CAPACITORS ±20%

VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

VLOAD REG 6, 7 13.2mVLSB

V2(ILOAD) REG 8, 9 1.223mA/LSB

TREMOTE REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

MMBT3904

RIN

20Ω

ILOAD

0A TO 10A

ROUT

4.99k

200k

4.75k

1% 0.1µF

RSENSE

1mΩ

–INF

V+

V–

LTC6102HV

OUT

VREG

+IN

VCC V1

LTC2990

2-WIRE

I2C

INTERFACE

GND

SDA

SCL

ADR0

ADR1

2990 TA02

0.1µF

470pF

MICROPROCESSOR

VCC V1

LTC2990

2-WIRE

I2C

INTERFACE

GND

SDA

SCL

ADR0

ADR1

2990 TA03

10.0k

3.3V

30.1k

12V

VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

V1 (+5) REG 6, 7 0.61mVLSB

V2(+12) REG 8, 9 1.22mV/LSB

TPROCESSOR REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

0.1µF

Computer Voltage and Temperature Monitoring

LTC2990

Rev. F

For more information www.analog.com

TYPICAL APPLICATIONS

Large Motor Protection/Regulation

VCC V1

LTC2990

LOADPWR = I • V

0.01Ω

1W, 1%

MOTOR CONTROL VOLTAGE

0V TO 40V

0A TO 10A

2-WIRE

I2C

INTERFACE

71.5k

10.2k

GND

470pF

TMOTOR

MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA05

MOTOR

TINTERNAL

VOLTAGE AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

VMOTOR REG 8, 9 2.44mVLSB

TMOTOR REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x59

TAMB REG 4, 5 0.0625°C/LSB

IMOTOR REG 6, 7 15.54mA/LSB

TMOTOR REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

0.1µF

Motor Protection/Regulation

VCC V1

LTC2990

LOADPWR = I • V

0.1Ω

MOTOR CONTROL VOLTAGE

0VDC TO 5VDC

0A TO ±2.2A

2-WIRE

I2C

INTERFACE

GND

470pF

TMOTOR

MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA04

MOTOR

TINTERNAL

CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x59

TAMB REG 4, 5 0.0625°C/LSB

IMOTOR REG 6, 7 194µA/LSB

TMOTOR REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

VOLTAGE AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

VMOTOR REG 8, 9 305.18µVLSB

TMOTOR REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

0.1µF

LTC2990

Rev. F

For more information www.analog.com

Fan/Air Filter/Temperature Alarm

VCC V1

LTC2990

2-WIRE

I2C

INTERFACE

3.3V

GND

470pF 22Ω

0.125W

HEATER

NDS351AN

TEMPERATURE FOR:

HEATER ENABLE

GOOD FAN

BAD FAN

FAN

MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA06

TINTERNAL

HEATER ENABLE

2 SECOND PULSE

CONTROL REGISTER: 0x5D

TAMB REG 4, 5 0.0625°C/LSB

TR1 REG 6, 7 0.0625°C/LSB

TR2 REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

470pF

3.3V

22Ω

0.125W

FAN

0.1µF

TYPICAL APPLICATIONS

VCC V1

LTC2990

BATTERY I AND V MONITOR

15mΩ*

CHARGING

CURRENT

2-WIRE

I2C

INTERFACE

GND

470pF NiMH

BATTERY

V(t)

100% 100%

• • •

TBATT

MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA07

TINTERNAL *IRC LRF3W01R015F

CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x59

TAMB REG 4, 5 0.0625°C/LSB

IBAT REG 6, 7 1.295mA/LSB

TBAT REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

VOLTAGE AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

VBAT REG 8, 9 305.18µVLSB

TBAT REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

+T(t)

100%

I(t)

0.1µF

Battery Monitoring

LTC2990

Rev. F

For more information www.analog.com

TYPICAL APPLICATIONS

Wet-Bulb Psychrometer

VCC V1

LTC2990

µC

GND

470pF

TDRY TWET

MMBT3904 MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA08

470pF

TINTERNAL DAMP MUSLIN

WATER

RESERVOIR

CONTROL REGISTER: 0x5D

TAMB REG 4, 5 0.0625°C/LSB

TWET REG 6, 7 0.0625°C/LSB

TDRY REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

∆T

NDS351AN

FAN ENABLE

FAN

FAN: SUNON

KDE0504PFB2

0.1µF

REFERENCES:

http://en.wikipedia.org/wiki/Hygrometer

http://en.wikipedia.org/wiki/Psychrometrics

Wind Direction/Instrumentation

VCC V1

LTC2990

3.3V

µC

GND

470pF

MMBT3904 MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA11

470pF

3.3V

HEATER

75Ω

0.125W

TINTERNAL

CONTROL REGISTER: 0x5D

TAMB REG 4, 5 0.0625°C/LSB

TR1 REG 8, 9 0.0625°C/LSB

TR2 REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

2N7002

HEATER ENABLE

2 SECOND PULSE

0.1µF

LTC2990

Rev. F

For more information www.analog.com

TYPICAL APPLICATIONS

Liquid-Level Indicator

VCC

LTC2990

3.3V

µC

GND

SDA

SCL

ADR0

ADR1

V2 470pF

3.3V

470pF

TINTERNAL

CONTROL REGISTER: 0x5D

TAMB REG 4, 5 0.0625°C/LSB

THI REG 6, 7 0.0625°C/LSB

TLO REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

NDS351AN

2290 TA09

HEATER: 75Ω 0.125W

*SENSOR MMBT3904, DIODE CONNECTED

SENSOR LO*

∆T = ~2.0°C pp, SENSOR HI

~0.2°C pp, SENSOR LO

SENSOR HI*

HEATER ENABLE

2 SECOND PULSE

HEATER ENABLE

SENSOR HI

SENSOR LO

0.1µF

Oscillator/Reference Oven Temperature Regulation

VCC V1

LTC2990

HEATERPWR = I •V

0.1Ω

HEATER

VOLTAGE

2-WIRE

I2C

INTERFACE

GND

470pF

FEED

FORWARD

FEED

BACK

HEATER

HEATER CONSTRUCTION:

5FT COIL OF #34 ENAMEL WIRE

~1.6Ω AT 70°C

PHEATER = ~0.4W WITH TA = 20°C

HEATER POWER = α • (TSET – TAMB) + β • ∫(TOVEN – TSET) dt

20°C

AMBIENT

STYROFOAM

INSULATION

70°C

OVEN

TOVEN

α = 0.004W, β = 0.00005W/DEG-s

MMBT3904

SDA

SCL

ADR0

ADR1

2990 TA10

TINTERNAL

CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x59

TAMB REG 4, 5 0.0625°C/LSB

IHEATER REG 6, 7 269µVLSB

THEATER REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

VOLTAGE AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

V1, V2 REG 8, 9 305.18µVLSB

TOVEN REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

0.1µF

LTC2990

Rev. F

For more information www.analog.com

PACKAGE DESCRIPTION

MS Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1661 Rev F)

MSOP (MS) 0213 REV F

0.53 ±0.152

(.021 ±.006)

SEATING

PLANE

0.18

(.007)

1.10

(.043)

MAX

0.17 –0.27

(.007 – .011)

TYP

0.86

(.034)

REF

0.50

(.0197)

BSC

1234 5

4.90 ±0.152

(.193 ±.006)

0.497 ±0.076

(.0196 ±.003)

REF

8910 76

3.00 ±0.102

(.118 ±.004)

(NOTE 3)

3.00 ±0.102

(.118 ±.004)

(NOTE 4)

NOTE:

1. DIMENSIONS IN MILLIMETER/(INCH)

2. DRAWING NOT TO SCALE

3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.

MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.

INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE

5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX

0.254

(.010) 0° – 6° TYP

DETAIL “A”

GAUGE PLANE

5.10

(.201)

MIN

3.20 – 3.45

(.126 – .136)

0.889 ±0.127

(.035 ±.005)

RECOMMENDED SOLDER PAD LAYOUT

0.305 ±0.038

(.0120 ±.0015)

TYP

0.50

(.0197)

BSC

0.1016 ±0.0508

(.004 ±.002)

MS Package

10-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1661 Rev F)

LTC2990

Rev. F

For more information www.analog.com

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog

Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications

subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 6/11 Revised title of data sheet from “I2C Temperature, Voltage and Current Monitor”

Revised Conditions and Values under Measurement Accuracy in Electrical Characteristics section

Revised curve G05 labels in Typical Performance Characteristics section

Revised Applications Information section and renumbered tables and table references

9 to 17

B 8/11 Updated Features section

Updated Current Measurements section

Updated Related Parts

C 12/11 Removed conditions for VCC(TUE) in Electrical Characteristics

Updated Pin 8 description

Removed ° symbol in reference to Kelvin measurements

Revised Current Measurements, Voltage/Current, I2C Device Addressing, Table2, Table5, and Table10 in

Applications Information

Revised Typical Applications drawings TA05 and TA11

10, 11, 12, 14,

15, 17

19, 20

D 7/14 Revised Device Configuration section

Updated MSOP Package Description

E 11/16 Added VOFFSET_DIFF and VOFFSET_SE to the Electrical Characteristics section 3

F 11/18 Corrected current register equations

Corrected differential voltage = +0.300 binary value

LTC2990

Rev. F

For more information www.analog.com

ANALOG DEVICES, INC. 2010-2018

11/18

www.analog.com

RELATED PARTS

TYPICAL APPLICATION

PART NUMBER DESCRIPTION COMMENTS

LTC2991 Octal I2C Voltage, Current, Temperature Monitor Remote and Internal Temperatures, 14-Bit Voltages and Current,

Internal 10ppm/°C Reference

LTC2997 Remote/Internal Temperature Sensor Temperature to Voltage with Integrated 1.8V Voltage Reference,

±1°C Accuracy

LM134 Constant Current Source and Temperature Sensor Can Be Used as Linear Temperature Sensor

LTC1392 Micropower Temperature, Power Supply and Differential

Voltage Monitor Complete Ambient Temperature Sensor Onboard

LTC2487 16-Bit, 2-/4-Channel Delta Sigma ADC with PGA, Easy Drive™

and I2C Interface Internal Temperature Sensor

LTC6102/LTC6102HV Precision Zero Drift Current Sense Amplifier 5V to 100V, 105V Absolute Maximum (LTC6102HV)

LTC2983 Multi-Sensor High Accuracy Digital Temperature

Measurement System 20 Channels Measure Any Combination of Thermocouples, RTDs,

Thermistors and Diodes

LTC2984 Multi-Sensor High Accuracy Digital Temperature

Measurement System with EEPROM 20 Channels Measure Any Combination of Thermocouples, RTDs,

Thermistors and Diodes

LTC2986 Multi-Sensor High Accuracy Digital Temperature

Measurement System with EEPROM 10 Channels Measure Any Combination of Thermocouples, RTDs,

Thermistors and Diodes

High Voltage/Current and Temperature Monitoring

–

–INS 0.1µF

VIN

5V TO 105V

0.1µF

470pF

ALL CAPACITORS ±20%

VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION:

CONTROL REGISTER: 0x58

TAMB REG 4, 5 0.0625°C/LSB

VLOAD REG 6, 7 13.2mVLSB

V2(ILOAD) REG 8, 9 1.223mA/LSB

TREMOTE REG A, B 0.0625°C/LSB

VCC REG E, F 2.5V + 305.18µV/LSB

MMBT3904

RIN

20Ω

ILOAD

0A TO 10A

ROUT

4.99k

200k

4.75k

1% 0.1µF

RSENSE

1mΩ

–INF

V+

V–

LTC6102HV

OUT

VREG

+IN

VCC V1

LTC2990

2-WIRE

I2C

INTERFACE

GND

SDA

SCL

ADR0

ADR1

2990 TA02

0.1µF