2008-2013 Microchip Technology Inc. DS20002090C-page 1
MCP73871
Features
• Integrated System Load Sharing and Battery
Charge Management
- Simultaneously Power the System and
Charge the Li-Ion Battery
- Voltage Proportional Current Control (VPCC)
ensures system load has priority over Li-Ion
battery charge current
- Low-Loss Power-Path Management with
Ideal Diode Operation
• Complete Linear Charge Management Controller
- Integrated Pass Transistors
- Integrated Current Sense
- Integrated Reverse Discharge Protection
- Selectable Input Power Sources: USB Port or
AC-DC Wall Adapter
• Preset High Accuracy Charge Voltage Options:
- 4.10V, 4.20V, 4.35V or 4.40V
- ±0.5% Regulation Tolerance
• Constant Current/Constant Voltage (CC/CV)
Operation with Thermal Regulation
• Maximum 1.8A Total Input Current Control
• Resistor Programmable Fast Charge Current
Control: 50 mA to 1A
• Resistor Programmable Termination Set Point
• Selectable USB Input Current Control
- Absolute Maximum: 100 mA (L)/500 mA (H)
• Automatic Recharge
• Automatic End-of-Charge Control
• Safety Timer With Timer Enable/Disable Control
• 0.1C Preconditioning for Deeply Depleted Cells
• Battery Cell Temperature Monitor
• Undervoltage Lockout (UVLO)
• Low Battery Status Indicator (LBO)
• Power-Good Status Indicator (PG)
• Charge Status and Fault Condition Indicators
• Numerous Selectable Options Available for a
Variety of Applications:
- Refer to Section 1.0 “Electrical
Characteristics” for Selectable Options
- Refer to the Product Identification System
for Standard Options
• Temperature Range: -40°C to +85°C
• Packaging: 20-Lead QFN (4 mm x 4 mm)
Applications
• GPSs/Navigators
• PDAs and Smart Phones
• Portable Media Players and MP3 Players
• Digital Cameras
• Bluetooth Headsets
• Portable Medical Devices
• Charge Cradles/Docking Stations
• Toys
Description
The MCP73871 device is a fully integrated linear
solution for system load sharing and Li-Ion/Li-Polymer
battery charge management with AC-DC wall adapter
and USB port power sources selection. It is also
capable of autonomous power source selection
between input and battery. Along with its small physical
size, the low number of required external components
makes the device ideally suited for portable
applications.
The MCP73871 device automatically obtains power for
the system load from a single-cell Li-Ion battery or an
input power source (AC-DC wall adapter or USB port).
The MCP73871 device specifically adheres to the
current drawn limits governed by the USB specification.
With an AC-DC wall adapter providing power to the
system, an external resistor sets the magnitude of 1A
maximum charge current while supporting up to 1.8A
total current for system load and battery charge
current.
The MCP73871 device employs a constant-
current/constant-voltage (CC/CV) charge algorithm
with selectable charge termination point. To
accommodate new and emerging battery charging
requirements, the constant voltage regulation is fixed
with four available options: 4.10V, 4.20V, 4.35V or
4.40V. The MCP73871 device also limits the charge
current based on the die temperature during high
power or high ambient conditions. This thermal
regulation optimizes the charge cycle time while
maintaining device reliability.
The MCP73871 device includes a low battery indicator,
a power-good indicator and two charge status
indicators that allow for outputs with LEDs or
communication with host microcontrollers. The
MCP73871 device is fully specified over the ambient
temperature range of -40°C to +85°C.
Stand-Alone System Load Sharing and Li-Ion/Li-Polymer Battery Charge
Management Controller
MCP73871
DS20002090C-page 2 2008-2013 Microchip Technology Inc.
Package Types
Typical Application Circuit
IN
STAT1/LBO
PG
THERM
STAT2
PROG1
IN
OUT
OUT
CE
SEL
PROG3
TE
VBAT
VBAT
VPCC
VSS
VSS VBAT_SENSE
2EP
20
1
19 18 17
3
412
11
10
9
5
678
13
14
15
16
21
PROG2
MCP73871
20-Lead QFN*
* Includes Exposed Thermal Pad (EP); see Table 3-1.
STAT1
LBO
IN OUT
PG
VBAT
Single-Cell
Li-Ion Battery
7
1, 20
8
18, 19
10 μF
10, 11, EP
AC-DC Adapter
or
USB Port
STAT2 THERM
VSS
PROG1
PROG3 12
13 RPROG1
6
5
14, 15, 16
470
470
470
24.7 μF
System
Load
SEL
TE
PROG2
Hi
Low
Hi
Low
Hi
Low
3
4
9
RPROG3
VPCC
NTC
10 k
Hi
Low
17 CE
4.7 μF
MCP73871 Typical Application
2008-2013 Microchip Technology Inc. DS20002090C-page 3
MCP73871
Functional Block Diagram
STAT1
PROG1
VBAT
G = 0.001
VSS
Direction
Control
TERM
+
-
+
-
LTVT
+
-
HTVT
THERM
50 μA
UVLO,
REFERENCE,
CHARGE
CONTROL,
TIMER,
AND
STATUS
LOGIC
STAT2
PG
Direction
Control
PROG2
IN
+
-
CURRENT
LIMIT
VREF
+
-
CURRENT
LIMIT
VREF/2
PROG3
+
-
CA
VREF
PRECONDITION
+
-
VREF
+
-
VA
VREF
VREF
SEL
OUT
VREF
TE
0.2
0.2Ideal
Diode,
Synchronous
Switch
CHRG
+
-
VREF
+
-
VREF
VPCC
CE
VBAT_SENSE
G = 0.001
G = 0.001
G = 0.001
VREF (1.21V)
361k
190k
7k
89k
MCP73871
DS20002090C-page 4 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 5
MCP73871
1.0 ELECTRICAL
CHARACTERISTICS
Absolute Maximum Ratings†
VIN....................................................................................7.0V
All Inputs and Outputs w.r.t. ................ VSS-0.3V to VDD+0.3V
(VDD = VIN or VBAT)
Maximum Junction Temperature, TJ............Internally Limited
Storage temperature .....................................-65°C to +150°C
ESD protection on all pins
Human Body Model (1.5 k in Series with 100 pF)4 kV
Machine Model (200 pF, No Series Resistance) .............300V
† Notice: Stresses above those listed under “Maximum
Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of
the device at those or any other conditions above those
indicated in the operational listings of this specification
is not implied. Exposure to maximum rating conditions
for extended periods may affect device reliability.
DC CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = VREG + 0.3V to 6V, TA = -40°C to +85°C.
Typical values are at +25°C, VIN = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
Supply Input
Supply Voltage VIN VREG + 0.3V — 6 V
Supply Current ISS — 2500 3750 μA Charging
— 260 350 μA Charge Complete
— 180 300 μA Standby
—2850μA Shutdown
(VDD < VBAT – 100 mV or
VDD < VSTOP)
UVLO Start Threshold VSTART VREG + 0.05V VREG + 0.15V VREG + 0.25V V VDD = Low-to-High
UVLO Stop Threshold VSTOP VREG – 0.07V VREG + 0.07V VREG + 0.17V V VDD = High-to-Low
UVLO Hysteresis VHYS —90—mV
Voltage Regulation (Constant Voltage Mode)
Regulated
Charge Voltage
VREG 4.080 4.10 4.121 V VDD = [VREG(typical) + 1V]
IOUT = 10 mA
TA = -5°C to +55°C
4.179 4.20 4.221 V
4.328 4.35 4.372 V
4.378 4.40 4.422
Regulated Charge
Voltage Tolerance
VRTOL -0.5 — +0.5 % TA = +25°C
-0.75 — +0.75 % TA = -5°C to +55°C
Line Regulation VBAT/VBAT)
/
VDD|
— 0.08 0.20 %/V VDD = [VREG(typical) + 1V] to 6V
IOUT = 10 mA
Load Regulation VBAT/VBAT| — 0.08 0.18 % IOUT = 10 mA to 150 mA
VDD = [VREG(typical) + 1V]
Supply Ripple
Attenuation
PSRR — -47 — dB IOUT = 10 mA, 1 kHz
— -40 — dB IOUT = 10 mA, 10 kHz
Note 1: The value is ensured by design and not production tested.
2: The maximum available charge current is also limited by the value set at PROG1 input.
MCP73871
DS20002090C-page 6 2008-2013 Microchip Technology Inc.
Current Regulation (Fast Charge Constant Current Mode)
AC-Adapter
Fast Charge
Current
IREG 90 100 110 mA PROG1 = 10 k
TA = -5°C to +55°C, SEL = Hi
900 1000 1100 mA PROG1 = 1 k
TA = -5°C to +55°C, SEL = Hi
USB Fast Charge
Current
IREG 80 90 100 mA PROG2 = Low, SEL = Low,
(Note 2)
TA = -5°C to +55°C
400 450 500 mA PROG2 = High, SEL = Low,
(Note 2)
TA = -5°C to +55°C
Input Current Limit Control (ICLC)
USB-Port Supply
Current Limit
ILIMIT_USB 80 90 100 mA PROG2 = Low, SEL = Low
TA = -5°C to +55°C
400 450 500 mA PROG2 = High, SEL = Low
TA = -5°C to +55°C
AC-DC Adapter Current
Limit
ILIMIT_AC 1500 1650 1800 mA SEL = High, TA = -5°C to +55°C
Voltage Proportional Charge Control (VPCC - Input Voltage Regulation)
VPCC Input Threshold VVPCC — 1.23 — V IOUT = 10 mA
TA = -5°C to +55°C
VPCC Input Threshold
Tolerance
VRTOL -3 — +3 %
Input Leakage Current ILK — 0.01 1 μAV
VPCC = VDD
Precondition Current Regulation (Trickle Charge Constant Current Mode)
Precondition Current
Ratio
IPREG/IREG 7.5 10 12.5 % PROG1 = 1.0 k to 10 k
TA = -5°C to +55°C
Precondition Current
Threshold Ratio
VPTH/VREG 69 72 75 % VBAT Low-to-High
Precondition Hysteresis VPHYS — 105 — mV VBAT High-to-Low
Automatic Charge Termination Set Point
Charge Termination
Current Ratio
ITERM 75 100 125 mA PROG3 = 10 k
TA = -5°C to +55°C
7.5 10 12.5 mA PROG3 = 100 k
TA = -5°C to +55°C
Automatic Recharge
Recharge Voltage
Threshold Ratio
VRTH VREG – 0.21V VREG – 0.15V VREG – 0.09V V VBAT High-to-Low
IN-to-OUT Pass Transistor ON-Resistance
ON-Resistance RDS_ON — 200 — mVDD = 4.5V, TJ = 105°C
DC CHARACTERISTICS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = VREG + 0.3V to 6V, TA = -40°C to +85°C.
Typical values are at +25°C, VIN = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
Note 1: The value is ensured by design and not production tested.
2: The maximum available charge current is also limited by the value set at PROG1 input.
2008-2013 Microchip Technology Inc. DS20002090C-page 7
MCP73871
Charge Transistor ON-Resistance
ON-Resistance RDSON_ — 200 — mVDD = 4.5V, TJ = 105°C
BAT-to-OUT Pass Transistor ON-Resistance
ON-Resistance RDS_ON — 200 — mVDD = 4.5V, TJ = 105°C
Battery Discharge Current
Output Reverse
Leakage Current
IDISCHARGE —3040μA Shutdown
(VBAT < VDD < VUVLO)
—3040μA Shutdown (0 < VDD < VBAT)
—3040μAV
BAT = Power Out, No Load
— -6 -13 μA Charge Complete
Status Indicators - STAT1 (LBO), STAT2, PG
Sink Current ISINK —1635mA
Low Output Voltage VOL — 0.4 1 V ISINK = 4 mA
Input Leakage Current ILK — 0.01 1 μA High Impedance, VDD on pin
Low Battery Indicator (LBO)
Low Battery Detection
Threshold
VLBO — Disable — VBAT > VIN, PG = Hi-Z
TA = -5°C to +55°C
2.85 3.0 3.15 V
2.95 3.1 3.25 V
3.05 3.2 3.35 V
Low Battery Detection
Hysteresis
VLBO_HYS — 150 — mV VBAT Low-to-High
PROG1 Input (PROG1)
Charge Impedance
Range
RPROG 1 — 20 k
PROG3 Input (PROG3)
Termination Impedance
Range
RPROG 5 — 100 k
PROG2 Input (PROG2)
Input High Voltage Level VIH 1.8 — — V
Input Low Voltage Level VIL — — 0.8 V
Input Leakage Current ILK — 0.01 1 μAV
PROG2 = VDD
Timer Enable (TE)
Input High Voltage Level VIH 1.8 — — V Note 1
Input Low Voltage Level VIL — — 0.8 V Note 1
Input Leakage Current ILK — 0.01 1 μAV
TE = VDD
DC CHARACTERISTICS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = VREG + 0.3V to 6V, TA = -40°C to +85°C.
Typical values are at +25°C, VIN = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
Note 1: The value is ensured by design and not production tested.
2: The maximum available charge current is also limited by the value set at PROG1 input.
MCP73871
DS20002090C-page 8 2008-2013 Microchip Technology Inc.
Chip Enable (CE)
Input High Voltage Level VIH 1.8 — — V
Input Low Voltage Level VIL — — 0.8 V
Input Leakage Current ILK — 0.01 1 μAV
CE = VDD
Input Source Selection (SEL)
Input High Voltage Level VIH 1.8 — — V
Input Low Voltage Level VIL — — 0.8 V
Input Leakage Current ILK — 0.01 1 μAV
SEL = VDD
Thermistor Bias
Thermistor Current
Source
ITHERM 47 50 53 μA2 k < RTHERM < 50 k
Thermistor Comparator
Upper Trip Threshold VT1 1.20 1.24 1.26 V VT1 Low-to-High
Upper Trip Point
Hysteresis
VT1HYS — -40 — mV
Lower Trip Threshold VT2 0.23 0.25 0.27 V VT2 High-to-Low
Lower Trip Point
Hysteresis
VT2HYS —40—mV
Thermal Shutdown
Die Temperature TSD — 150 — C
Die Temperature
Hysteresis
TSDHYS —10—C
DC CHARACTERISTICS (CONTINUED)
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = VREG + 0.3V to 6V, TA = -40°C to +85°C.
Typical values are at +25°C, VIN = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
Note 1: The value is ensured by design and not production tested.
2: The maximum available charge current is also limited by the value set at PROG1 input.
2008-2013 Microchip Technology Inc. DS20002090C-page 9
MCP73871
AC CHARACTERISTICS
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = 4.6V to 6V.
Typical values are at +25°C, VDD = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
UVLO Start Delay tSTART —— 5 msV
DD Low-to-High
Current Regulation
Transition Time Out of Precondition tDELAY — — 10 ms VBAT < VPTH to VBAT > VPTH
Current Rise Time Out of Precondition tRISE — — 10 ms IOUT Rising to 90% of IREG
Precondition Comparator Filter Time tPRECON 0.4 1.3 3.2 ms Average VBAT Rise/Fall
Termination Comparator Filter Time tTERM 0.4 1.3 3.2 ms Average IOUT Falling
Charge Comparator Filter Time tCHARGE 0.4 1.3 3.2 ms Average VBAT Falling
Thermistor Comparator Filter Time tTHERM 0.4 1.3 3.2 ms Average THERM Rise/Fall
Elapsed Timer
Elapsed Timer Period tELAPSED — 0 — Hours
3.6 4.0 4.4 Hours
5.4 6.0 6.6 Hours
7.2 8.0 8.8 Hours
Status Indicators
Status Output Turn-off tOFF — — 500 μsI
SINK = 1 mA to 0 mA
Status Output Turn-on tON — — 500 μsI
SINK = 0 mA to 1 mA
Note 1: Internal safety timer is tested based on internal oscillator frequency measurement.
TEMPERATURE SPECIFICATIONS
Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = 4.6V to 6V.
Typical values are at +25°C, VDD = [VREG (typical) + 1.0V]
Parameters Sym Min Typ Max Units Conditions
Temperature Ranges
Specified Temperature Range TA-40 — +85 °C
Operating Temperature Range TJ-40 — +125 °C
Storage Temperature Range TA-65 — +150 °C
Thermal Package Resistances
Thermal Resistance, 20LD-QFN, 4x4 JA — 50 — °C/W 4-Layer JC51-7 Standard Board,
Natural Convection
JC —8— —
MCP73871
DS20002090C-page 10 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 11
MCP73871
2.0 TYPICAL PERFORMANCE CURVES
Note: Unless otherwise indicated, VIN = [VREG(typical) + 1V], IOUT = 10 mA and TA = +25°C, Constant Voltage mode.
FIGURE 2-1: Battery Regulation Voltage
(VBAT) vs. Supply Voltage (VDD).
FIGURE 2-2: Battery Regulation Voltage
(VBAT) vs. Ambient Temperature (TA).
FIGURE 2-3: Charge Current (IOUT) vs.
Programming Resistor (RPROG).
FIGURE 2-4: Charge Current (IOUT) vs.
Battery Regulation Voltage (VBAT).
FIGURE 2-5: Output Leakage Current
(IDISCHARGE) vs. Ambient Temperature (TA).
FIGURE 2-6: Output Leakage Current
(IDISCHARGE) vs. Battery Regulation Voltage
(VBAT).
Note: The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
MCP73871
DS20002090C-page 12 2008-2013 Microchip Technology Inc.
Note: Unless otherwise indicated, VIN = [VREG(typical) + 1V], IOUT = 10 mA and TA = +25°C, Constant Voltage mode.
FIGURE 2-7: Output Leakage Current
(IDISCHARGE) vs. Battery Voltage (VBAT).
FIGURE 2-8: Charge Current (IOUT) vs.
Supply Voltage (VDD).
FIGURE 2-9: Charge Current (IOUT) vs.
Supply Voltage (VDD).
FIGURE 2-10: Charge Current (IOUT) vs.
Supply Voltage (VDD).
FIGURE 2-11: Charge Current (IOUT) vs.
Ambient Temperature (TA).
FIGURE 2-12: Charge Current (IOUT) vs.
Ambient Temperature (TA).
2008-2013 Microchip Technology Inc. DS20002090C-page 13
MCP73871
Note: Unless otherwise indicated, VIN = [VREG(typical) + 1V], IOUT = 10 mA and TA = +25°C, Constant Voltage mode.
FIGURE 2-13: Charge Current (IOUT) vs.
Ambient Temperature (TA).
FIGURE 2-14: Charge Current (IOUT) vs.
Junction Temperature (TJ).
FIGURE 2-15: Charge Current (IOUT) vs.
Junction Temperature (TJ).
FIGURE 2-16: Charge Current (IOUT) vs.
Junction Temperature (TJ).
FIGURE 2-17: Thermistor Current (ITHERM)
vs. Supply Voltage (VDD).
FIGURE 2-18: Thermistor Current (ITHERM)
vs. Ambient Temperature (TA).
MCP73871
DS20002090C-page 14 2008-2013 Microchip Technology Inc.
Note: Unless otherwise indicated, VIN = [VREG(typical) + 1V], IOUT = 10 mA and TA = +25°C, Constant Voltage mode.
FIGURE 2-19: Power Supply Ripple
Rejection (PSRR).
FIGURE 2-20: Line Transient Response.
IOUT = 100 mA.
FIGURE 2-21: Line Transient Response.
IOUT = 500 mA.
FIGURE 2-22: Load Transient Response.
IOUT = 100 mA.
FIGURE 2-23: Load Transient Response.
IOUT = 500 mA.
FIGURE 2-24: Undervoltage Lockout.
2008-2013 Microchip Technology Inc. DS20002090C-page 15
MCP73871
Note: Unless otherwise indicated, VIN = [VREG(typical) + 1V], IOUT = 10 mA and TA = +25°C, Constant Voltage mode.
FIGURE 2-25: Startup Delay.
FIGURE 2-26: Complete Charge Cycle
(130 mAh Li-Ion Battery).
FIGURE 2-27: Complete Charge Cycle
(1000 mAh Li-Ion Battery).
FIGURE 2-28: Typical Charge Profile in
Preconditioning (1000 mAh Battery).
MCP73871
DS20002090C-page 16 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 17
MCP73871
3.0 PIN DESCRIPTION
The descriptions of the pins are listed in Table 3-1.
3.1 Power Supply Input (IN)
A supply voltage of VREG + 0.3V to 6V is
recommended. Bypass to VSS with a minimum of
4.7 μF.
3.2 System Output Terminal (OUT)
The MCP73871 device powers the system via output
terminals while independently charging the battery.
This feature reduces the charge and discharge cycles
on the battery, allowing proper charge termination and
the system to run with an absent or defective battery
pack. It also gives the system priority on input power,
allowing the system to power up with deeply depleted
battery packs. Bypass to VSS with a minimum of 4.7 μF
is recommended.
3.3 Voltage Proportional Charge
Control (VPCC)
If the voltage on the IN pin drops to a preset value,
determined by the threshold established at the VPCC
input, due to a limited amount of input current or input
source impedance, the battery charging current is
reduced. If possible, further demand from the system is
supported by the battery. To enable this feature, simply
supply 1.23V or greater to the VPCC pin. This feature
can be disabled by connecting the VPCC pin to IN.
For example, a system is designed with a 5.5V rated
DC power supply with ±0.5V tolerance. The worst
condition of 5V is selected, which is used to calculate
the VPCC supply voltage with divider.
TABLE 3-1: PIN FUNCTION TABLE
Pin
Number Symbol I/O Function
1, 20 OUT O System Output Terminal
2 VPCC I Voltage proportional charge control
3 SEL I Input type selection (Low for USB port, High for AC-DC adapter)
4 PROG2 I USB port input current limit selection when SEL = Low
(Low = 100 mA, High = 500 mA)
5 THERM I/O Thermistor monitoring input and bias current
6PG O Power-Good Status Output (Open-Drain)
7 STAT2 O Charge Status Output 2 (Open-Drain)
8 STAT1/LBO O Charge Status Output 1 (Open-Drain). Low battery output indicator when
VBAT > VIN
9 TE I Timer Enable; Enables Safety Timer when active Low
10, 11, EP VSS — Battery Management 0V Reference. EP (Exposed Thermal Pad).
There is an internal electrical connection between the exposed thermal pad and
VSS. The EP must be connected to the same potential as the VSS pin on the
Printed Circuit Board (PCB)
12 PROG3 I/O Termination set point for both AC-DC adapter and USB port
13 PROG1 I/O Fast charge current regulation setting with SEL = High. Preconditioning set point
for both USB port and AC-DC adapter
14, 15 VBAT I/O Battery Positive Input and Output connection
16 VBAT_SENSE I/O Battery Voltage Sense
17 CE I Device Charge Enable; Enabled when CE = High
18, 19 IN I Power Supply Input
Legend: I = Input, O = Output, I/O = Input/Output
Note: To ensure proper operation, the input pins must not allow floating and should always tie to either High or
Low.
MCP73871
DS20002090C-page 18 2008-2013 Microchip Technology Inc.
The voltage divider equation is shown below:
EQUATION 3-1:
The calculated R1 equals 337.2 k when 110 k is
selected for R2. The 330 k resistor is selected for R1
to build the voltage divider for VPCC.
FIGURE 3-1: Voltage Divider Example.
3.4 Input Source Type Selection (SEL)
The input source type selection (SEL) pin is used to
select input power source for input current limit control
feature. With the SEL input High, the MCP73871
device is capable of providing 1.65 (typical) total
amperes to be shared by the system load and Li-Ion
battery charging. The MCP73871 device limits the
input current up to 1.8A. When SEL active Low, the
input source is designed to provide system power and
Li-Ion battery charging from a USB Port input while
adhering to the current limits governed by the USB
specification.
3.5 Battery Management 0V Reference
(VSS)
Connect to negative terminal of the battery, system
load and input supply.
3.6 Battery Charge Control Output
(VBAT)
Connect to positive terminal of the Li-Ion/Li-Polymer
battery. Bypass to VSS with a minimum of 4.7 μF to
ensure loop stability when the battery is disconnected.
3.7 Battery Voltage Sense
(VBAT_SENSE)
Connect to positive terminal of battery. A precision
internal voltage sense regulates the final voltage on
this pin to VREG.
3.8 Charge Current Regulation Set
(PROG1)
The maximum constant charge current is set by placing
a resistor from PROG1 to VSS. PROG1 sets the
maximum constant charge current for both AC-DC
adapter and USB port. However, the actual charge
current is based on the input source type and the
system load requirement.
3.9 USB-Port Current Regulation Set
(PROG2)
The MCP73871 device USB-Port current regulation set
input (PROG2) is a digital input selection. A logic Low
selects a one unit load input current from the USB port
(100 mA) while a logic High selects a five unit load input
current from the USB port (500 mA).
3.10 Charge Status Output 1 (STAT1)
STAT1 is an open-drain logic output for connection to
an LED for charge status indication. Alternatively, a
pull-up resistor can be applied for interfacing to a host
microcontroller. Refer to Table 5-1 for a summary of the
status output during a charge cycle.
3.11 Charge Status Output 2 (STAT2)
STAT2 is an open-drain logic output for connection to
an LED for charge status indication. Alternatively, a
pull-up resistor can be applied for interfacing to a host
microcontroller. Refer to Table 5-1 for a summary of the
status output during a charge cycle.
3.12 Power-Good (PG)
The power-good (PG) is an open-drain logic output for
input power supply indication. The PG output is low
whenever the input to the MCP73871 device is above
the UVLO threshold and greater than the battery
voltage. The PG output may be used with an LED or as
an interface to a host microcontroller to signal when an
input power source is supplying power to the system
and the battery. Refer to Table 5-1 for a summary of the
status output during a charge cycle.
VVPCC
R2
R1R2
+
-------------------
VIN 1.23V==
1.23V 110k
110kR1
+
------------------------------
5V=
R1337.2k=
330 k
110 k
VIN
VPCC
2008-2013 Microchip Technology Inc. DS20002090C-page 19
MCP73871
3.13 Low Battery Output (LBO)
STAT1 also serves as low battery output (LBO) if the
selected MCP73871 is equipped with this feature. It
provides an indication to the system or end user when
the Li-Ion battery voltage level is low. The LBO feature
is enabled when the system is running from the Li-Ion
battery. The LBO output may be used with an LED or
as an interface to a host microcontroller to signal when
the system is operating from the battery and the battery
is running low on charge. Refer to Table 5-1 for a
summary of the status output during a charge cycle.
3.14 Timer Enable (TE)
The timer enable (TE) feature is used to enable or
disable the internal timer. A low signal enables and a
high signal disables the internal timer on this pin. The
TE input can be used to disable the timer when the sys-
tem load is substantially limiting the available supply
current to charge the battery. The TE input is compati-
ble with 1.8V logic.
3.15 Battery Temperature Monitor
(THERM)
The MCP73871 device continuously monitors battery
temperature during a charge cycle by measuring the
voltage between the THERM and VSS pins. An internal
50 μA current source provides the bias for most
common 10 k Negative Temperature Coefficient
(NTC) thermistors. The MCP73871 device compares
the voltage at the THERM pin to factory set thresholds
of 1.24V and 0.25V, typically. Once a voltage outside
the thresholds is detected during a charge cycle, the
MCP73871 device immediately suspends the charge
cycle. The charge cycle resumes when the voltage at
the THERM pin returns to the normal range. The
charge temperature window can be set by placing fixed
value resistors in series-parallel with a thermistor.
Refer to Section 6.0 “Applications” for calculations
of resistance values.
3.16 Charge Enable (CE)
With the CE input Low, the Li-Ion battery charger
feature of the MCP73871 is disabled. The charger fea-
ture is enabled when CE is active High. Allowing the
CE pin to float during the charge cycle may cause
system instability. The CE input is compatible with 1.8V
logic. Refer to Section 6.0 “Applications” for various
applications in designing with CE features.
3.17 Exposed Thermal Pad (EP)
An internal electrical connection exists between the
Exposed Thermal Pad (EP) and the VSS pin. They must
be connected to the same potential on the Printed
Circuit Board (PCB).
Note: The built-in safety timer is available for the
following options: 4 HR, 6 HR and 8 HR.
MCP73871
DS20002090C-page 20 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 21
MCP73871
4.0 DEVICE OVERVIEW
The MCP73871 device is a simple but fully integrated
linear charge management controller with system load
sharing feature. Figure 4-1 depicts the operational flow
algorithm.
FIGURE 4-1: MCP73871 Device Flow Chart.
SHUTDOWN MODE *
VDD < VUVLO
VDD < VBAT
STAT1 = Hi-Z
STAT2 = Hi-Z
PG = Hi-Z
PRECONDITIONING MODE
Charge Current = IPREG
STAT1 = LOW
STAT2 = Hi-Z
PG = LOW
Timer Reset
CONSTANT VOLTAGE MODE
Charge Voltage = VREG
STAT1 = LOW
PG = LOW
VBAT > VPTH
CHARGE COMPLETE MODE
No Charge Current
STAT1 = Hi-Z
STAT2 = LOW
PG = LOW
Timer Reset
IBAT < ITERM
Timer Expired
VBAT < VPTH
STANDBY MODE *
VBAT > (VREG + 100 mV)
CE = LOW
STAT1 = Hi-Z
STAT2 = Hi-Z
PG = LOW
* Continuously Monitored
TEMPERATURE FAULT
No Charge Current
STAT1 = LOW
STAT2 = LOW
PG = LOW
Timer Suspended
TIMER FAULT
No Charge Current
STAT1 = LOW
STAT2 = LOW
PG = LOW
Timer Expired
LBO *
VIN < VBAT
STAT1 = LOW
STAT2 = Hi-Z
PG = Hi-Z
VBAT > VPTH
STAT2 = Hi-Z
Timer Reset
FAST CHARGE MODE
Charge Current = IREG
STAT1 = LOW
STAT2 = Hi-Z
PG = LOW
Timer Enabled
MCP73871
DS20002090C-page 22 2008-2013 Microchip Technology Inc.
Table 4-1 shows the chip behavior based upon the operating conditions.
TABLE 4-1: CHIP BEHAVIOR REFERENCE TABLE
4.1 UnderVoltage Lockout (UVLO)
An internal undervoltage lockout (UVLO) circuit
monitors the input voltage and keeps the charger in
shutdown mode until the input supply rises above the
UVLO threshold.
In the event a battery is present when the input power
is applied, the input supply must rise approximately
100 mV above the battery voltage before the
MCP73871 device becomes operational.
The UVLO circuit places the device in Shutdown mode
if the input supply falls to within approximately 100 mV
of the battery voltage.
The UVLO circuit is always active. At any time the input
supply is below the UVLO threshold or falls within
approximately 100 mV of the voltage at the VBAT pin,
the MCP73871 device is placed in Shutdown mode.
During any UVLO condition, the battery reverse
discharge current is less than 2 μA.
4.2 System Load Sharing
The system load sharing feature gives the system
output pin (OUT) priority, allowing the system to power
up with deeply depleted battery packs.
With the SEL input active Low, the MCP73871 device
is designed to provide system power and Li-Ion battery
charging from a USB input while adhering to the current
limits governed by the USB specification.
With the SEL input active High, the MCP73871 device
limits the total supply current to 1.8A (system power
and charge current combined).
FIGURE 4-2: System Load Sharing
Diagram.
4.3 Charge Qualification
For a charge cycle to begin, all UVLO conditions must
be met and a battery or output load must be present.
A charge current programming resistor must be
connected from PROG1 to VSS when SEL = High.
When SEL = Low, PROG2 needs to be tied High or
Low for proper operation.
VIN ? VBAT
VIN > 2V
VIN > UVLO
CE VBAT ? VOUT State
Bias + VREF
Thermal
Block
Synchronous
Diode
IOUT
Charge
1
VBAT > VIN 00
0
—
Shutdown OFF
OFF
2 1 Battery
powered
system
ON
3VIN > VBAT 0 0 X — Shutdown OFF
4
VIN > VBAT 1
0
0
—
Shutdown
ON
OFF
OFF
5
1
Battery
powered
system
ON
6
1
0
VBAT < VOUT Standby
ON
OFF
ON
OFF
7
VBAT > VOUT
IN + BAT
powered
system
ON
8
1
VBAT < VOUT
IN powered,
Charge
possible
OFF ON/OFF
9
VBAT > VOUT
IN + BAT
powered
system
ON OFF
0.2Ideal
Diode,
Synchronous
Switch
Direction
Control
0.2
Current
Limit
Direction
Control
Charge
FET
System
Power
FET
VBAT
IN OUT
Charge
Control
2008-2013 Microchip Technology Inc. DS20002090C-page 23
MCP73871
4.4 Preconditioning
If the voltage at the VBAT pin is less than the
preconditioning threshold, the MCP73871 device
enters a preconditioning mode. The preconditioning
threshold is factory set. Refer to Section 1.0
“Electrical Characteristics” for preconditioning
threshold options.
In this mode, the MCP73871 device supplies 10% of
the fast charge current (established with the value of
the resistor connected to the PROG1 pin) to the
battery.
When the voltage at the VBAT pin rises above the
preconditioning threshold, the MCP73871 device
enters the Constant Current (fast charge) mode.
4.5 Constant Current Mode – Fast
Charge
During the Constant Current mode, the programmed
charge current is supplied to the battery or load. The
charge current is established using a single resistor
from PROG1 to VSS. The program resistor and the
charge current are calculated using the following
equation:
EQUATION 4-1:
Constant Current mode is maintained until the voltage
at the VBAT pin reaches the regulation voltage, VREG.
When Constant Current mode is invoked, the internal
timer is reset.
4.5.1 TIMER EXPIRED DURING
CONSTANT CURRENT - FAST
CHARGE MODE
If the internal timer expires before the recharge voltage
threshold is reached, a timer fault is indicated and the
charge cycle terminates. The MCP73871 device
remains in this condition until the battery is removed. If
the battery is removed, the MCP73871 device enters
the Standby mode where it remains until a battery is
reinserted.
4.6 Constant Voltage Mode
When the voltage at the VBAT pin reaches the
regulation voltage, VREG, constant voltage regulation
begins. The regulation voltage is factory set to 4.10V
or 4.20V with a tolerance of ±0.5%.
4.7 Charge Termination
The Constant Voltage mode charge cycle terminates
either when the average charge current diminishes
below a threshold established by the value of the
resistor connected from PROG3 to VSS or when the
internal charge timer expires. When the charge cycle
terminates due to a fully charged battery, the charge
current is latched off and the MCP73871 device enters
the Charge Complete mode. A 1 ms filter time on the
termination comparator ensures that transient load
conditions do not result in premature charge cycle
termination. The timer period is factory set and can be
disabled. Refer to Section 1.0 “Electrical
Characteristics” for timer period options.
The program resistor and the charge current are
calculated using the following equation:
EQUATION 4-2:
The recommended PROG3 resistor values are
between 5 k and 100 k.
4.8 Automatic Recharge
The MCP73871 device continuously monitors the
voltage at the VBAT pin in the charge complete mode. If
the voltage drops below the recharge threshold,
another charge cycle begins and current is supplied
again to the battery or load. The recharge threshold is
factory set. Refer to Section 1.0 “Electrical
Characteristics” for recharge threshold options.
IREG
1000V
RPROG1
--------------------=
Where:
RPROG = kilo-ohms (k
IREG = milliampere (mA)
Note: Charge termination and automatic
recharge features avoid constantly
charging Li-Ion batteries, resulting in
prolonged battery life while maintaining
full cell capacity.
ITERMINATION
1000V
RPROG3
--------------------=
Where:
RPROG = kilo-ohms (k
IREG = milliampere (mA)
MCP73871
DS20002090C-page 24 2008-2013 Microchip Technology Inc.
4.9 Thermal Regulation
The MCP73871 device limits the charge current based
on the die temperature. The thermal regulation
optimizes the charge cycle time while maintaining
device reliability. Figure 4-3 depicts the thermal
regulation for the MCP73871 device. Refer to
Section 1.0 “Electrical Characteristics” for thermal
package resistances and Section 6.1.1.2 “Thermal
Considerations” for calculating power dissipation.
.
FIGURE 4-3: Thermal Regulation.
4.10 Thermal Shutdown
The MCP73871 device suspends charge if the die
temperature exceeds 150°C. Charging resumes when
the die temperature has cooled by approximately 10°C.
The thermal shutdown is a secondary safety feature in
the event that there is a failure within the thermal
regulation circuitry.
4.11 Temperature Qualification
The MCP73871 device continuously monitors battery
temperature during a charge cycle by measuring the
voltage between the THERM and VSS pins. An internal
50 μA current source provides the bias for most
common 10 k NTC thermistors. The MCP73871
device compares the voltage at the THERM pin to
factory set thresholds of 1.24V and 0.25V, typically.
Once a voltage outside the thresholds is detected
during a charge cycle, the MCP73871 device
immediately suspends the charge cycle. The
MCP73871 device suspends charging by turning off
the charge pass transistor and holding the timer value.
The charge cycle resumes when the voltage at the
THERM pin returns to the normal range.
4.12 Voltage Proportional Charge
Control (VPCC)
If the voltage on the IN pin drops to a preset value,
determined by the threshold established at the VPCC
input, due to a limited amount of input current or input
source impedance, the battery charging current is
reduced. The VPCC control tries to reach a steady
state condition where the system load has priority and
the battery is charged with the remaining current.
Therefore, if the system demands more current than
the input can provide, the ideal diode becomes
forward-biased and the battery may supplement the
input current to the system load.
The VPCC sustains the system load as its highest
priority. It does this by reducing the noncritical charge
current while maintaining the maximum power output of
the adapter. Further demand from the system is
supported by the battery, if possible.
The VPCC feature functions identically for USB port or
AC-DC adapter inputs. This feature can be disabled by
connecting the VPCC to IN pin.
4.13 Input Current Limit Control (ICLC)
If the input current threshold is reached, then the
battery charging current is reduced. The ICLC tries to
reach a steady state condition where the system load
has priority and the battery is charged with the
remaining current. No active control limits the current
to the system. Therefore, if the system demands more
current than the input can provide or the ICLC is
reached, the ideal diode becomes forward biased and
the battery may supplement the input current to the
system load.
The ICLC sustains the system load as its highest
priority. This is done by reducing the non-critical charge
current while adhering to the current limits governed by
the USB specification or the maximum AC-DC adapter
current supported. Further demand from the system is
supported by the battery, if possible.
FIGURE 4-4: Input Current Limit Control -
USB Port.
2008-2013 Microchip Technology Inc. DS20002090C-page 25
MCP73871
5.0 DETAILED DESCRIPTION
5.1 Analog Circuitry
5.1.1 LOAD SHARING AND LI-ION
BATTERY MANAGEMENT INPUT
SUPPLY (VIN)
The VIN input is the input supply to the MCP73871
device. The MCP73871 device can be supplied by
either AC Adapter (VAC) or USB Port (VUSB) with SEL
pin. The MCP73871 device automatically powers the
system with the Li-Ion battery when the VIN input is not
present.
5.1.2 FAST CHARGE CURRENT
REGULATION SET (PROG1)
For the MCP73871 device, the charge current
regulation can be scaled by placing a programming
resistor (RPROG1) from the PROG1 pin to VSS. The
program resistor and the charge current are calculated
using the following equation:
EQUATION 5-1:
The fast charge current is set for maximum charge
current from AC-DC adapter and USB port. The
preconditioning current is 10% (0.1C) of the fast charge
current.
5.1.3 BATTERY CHARGE CONTROL
OUTPUT (VBAT)
The battery charge control output is the drain terminal
of an internal P-channel MOSFET. The MCP73871
device provides constant current and voltage
regulation to the battery pack by controlling this
MOSFET in the linear region. The battery charge
control output should be connected to the positive
terminal of the battery pack.
5.1.4 TEMPERATURE QUALIFICATION
(THERM)
The MCP73871 device continuously monitors battery
temperature during a charge cycle by measuring the
voltage between the THERM and VSS pins. An internal
50 μA current source provides the bias for most
common 10 k NTC or Positive Temperature Coeffi-
cient (PTC) thermistors.The current source is con-
trolled, avoiding measurement sensitivity to
fluctuations in the supply voltage (VDD). The
MCP73871 device compares the voltage at the
THERM pin to factory set thresholds of 1.24V and
0.25V, typically. Once a voltage outside the thresholds
is detected during a charge cycle, the MCP73871
device immediately suspends the charge cycle.
The MCP73871 device suspends charge by turning off
the pass transistor and holding the timer value. The
charge cycle resumes when the voltage at the THERM
pin returns to the normal range.
If temperature monitoring is not required, place a
standard 10 k resistor from THERM to VSS.
5.2 Digital Circuitry
5.2.1 STATUS INDICATORS AND
POWER-GOOD (PG)
The charge status outputs have two different states:
Low-Impedance (L) and High-Impedance (Hi-Z). The
charge status outputs can be used to illuminate LEDs.
Optionally, the charge status outputs can be used as an
interface to a host microcontroller. Table 5-1
summarizes the state of the status outputs during a
charge cycle.
TABLE 5-1: STATUS OUTPUTS
IREG
1000V
RPROG1
--------------------=
Where:
RPROG = kilo-ohms (k
IREG = milliampere (mA)
CHARGE CYCLE STATE STAT1 STAT2 PG
Shutdown (VDD = VBAT) Hi-Z Hi-Z Hi-Z
Shutdown (VDD = IN) Hi-Z Hi-Z L
Shutdown (CE = L) Hi-Z Hi-Z L
Preconditioning L Hi-Z L
Constant Current L Hi-Z L
Constant Voltage L Hi-Z L
Charge Complete - Standby Hi-Z L L
Temperature Fault L L L
Timer Fault L L L
Low Battery Output L Hi-Z Hi-Z
No Battery Present Hi-Z Hi-Z L
No Input Power Present Hi-Z Hi-Z Hi-Z
MCP73871
DS20002090C-page 26 2008-2013 Microchip Technology Inc.
5.2.2 AC-DC ADAPTER AND USB PORT
POWER SOURCE REGULATION
SELECT (SEL)
With the SEL input Low, the MCP73871 device is
designed to provide system power and Li-Ion battery
charging from a USB input while adhering to the current
limits governed by the USB specification. The host
microcontroller has the option to select either
a 100 mA (L) or a 500 mA (H) current limit based on
the PROG2 input. With the SEL input High, the
MCP73871 device limits the input current to 1.8A. The
programmed charge current is established using a
single resistor from PROG1 to VSS when driving SEL
High.
5.2.3 USB PORT CURRENT
REGULATION SELECT (PROG2)
Driving the PROG2 input to a logic Low selects the low
USB port source current setting (maximum 100 mA).
Driving the PROG2 input to a logic High selects the
high USB port source current setting (maximum
500 mA).
5.2.4 POWER-GOOD (PG)
The power-good (PG) option is a pseudo open-drain
output. The PG output can sink current, but not source
current. The PG output must not be pulled up higher
than VIN because there is a diode path back to VIN. The
PG output is low whenever the input to the MCP73871
device is above the UVLO threshold and greater than
the battery voltage. The PG output can be used as an
indication to the system that an input source other than
the battery is supplying power.
5.2.5 TIMER ENABLE (TE) OPTION
The timer enable (TE) input option is used to enable or
disable the internal timer. A low signal on this pin
enables the internal timer and a high signal disables
the internal timer. The TE input can be used to disable
the timer when the charger is supplying current to
charge the battery and power the system load. The TE
input is compatible with 1.8V logic.
2008-2013 Microchip Technology Inc. DS20002090C-page 27
MCP73871
6.0 APPLICATIONS
The MCP73871 device is designed to operate in
conjunction with a host microcontroller or in
stand-alone applications. The MCP73871 device
provides the preferred charge algorithm for Lithium-Ion
and Lithium-Polymer cells. The algorithm uses
Constant Current mode followed by Constant Voltage
mode. Figure 6-1 depicts a typical stand-alone
MCP73871 application circuit, while Figure 6-2 and
Figure 6-3 depict the accompanying charge profile.
FIGURE 6-1: MCP73871Typical Stand-Alone Application Circuit with VPCC.
FIGURE 6-2: Typical Charge Profile
(1000 mAh Battery).
FIGURE 6-3: Typical Charge Profile in
Preconditioning (1000 mAh Battery).
STAT1
LBO
IN OUT
PG VBAT
Single-Cell
Li-Ion Battery
7
1, 20
8
18, 19
10 μF
10, 11, EP
5V AC-DC Adapter
or
USB Port
STAT2
THERM
VSS
PROG1
PROG3 12
13 RPROG1
6
5
14, 15, 16
470
470
470
2
4.7 μF
System
Load
SEL
TE
PROG2
Hi
Low
Hi
Low
Hi
Low
3
4
9
RPROG3
VPCC
NTC
10 k
Hi
Low
17 CE
4.7 μF
330 k
110 k
MCP73871 Device Typical Application
MCP73871
DS20002090C-page 28 2008-2013 Microchip Technology Inc.
6.1 Application Circuit Design
Due to the low efficiency of linear charging, the most
important factors are thermal design and cost, which
are a direct function of the input voltage, output current
and thermal impedance between the battery charger
and the ambient cooling air. The worst-case situation is
when the device has transitioned from the
Preconditioning mode to the Constant Current mode. In
this situation, the battery charger has to dissipate the
maximum power. A trade-off must be made between
the charge current, cost and thermal requirements of
the charger.
6.1.1 COMPONENT SELECTION
Selection of the external components in Figure 6-1 is
crucial to the integrity and reliability of the charging
system. The following discussion is intended as a guide
for the component selection process.
6.1.1.1 Charge Current
The preferred fast charge current for Lithium-Ion cells
should always follow references and guidances from
battery manufacturers. For example, a 1000 mAh
battery pack has a preferred fast charge current of
0.7C. Charging at 700 mA provides the shortest charge
cycle times without degradation to the battery pack
performance or life.
6.1.1.2 Thermal Considerations
The worst-case power dissipation in the battery
charger occurs when the input voltage is at the
maximum and the device has transitioned from the
Preconditioning mode to the Constant Current mode. In
this case, the power dissipation is:
EQUATION 6-1:
For example, power dissipation with a 5V, ±10% input
voltage source and 500 mA, ±10% fast charge current
is:
EXAMPLE 6-1:
This power dissipation with the battery charger in the
QFN-20 package causes thermal regulation to enter as
depicted. Alternatively, the 4 mm x 4 mm DFN package
could be utilized to reduce heat by adding vias on the
exposed pad.
6.1.1.3 External Capacitors
The MCP73871 device is stable with or without a
battery load. To maintain good AC stability in the Con-
stant Voltage mode, a minimum capacitance of 4.7 μF
is recommended to bypass the VBAT pin to VSS. This
capacitance provides compensation when there is no
battery load. In addition, the battery and
interconnections appear inductive at high frequencies.
These elements are in the control feedback loop during
Constant Voltage mode. Therefore, the bypass
capacitance may be necessary to compensate for the
inductive nature of the battery pack.
Virtually any good quality output filter capacitor can be
used, regardless of the capacitor’s minimum Effective
Series Resistance (ESR) value. The actual value of the
capacitor (and its associated ESR) depends on the
output load current. A 4.7 μF ceramic, tantalum or
aluminum electrolytic capacitor at the output is usually
sufficient to ensure stability for charge currents up to
1000 mA.
6.1.1.4 Reverse-Blocking Protection
The MCP73871 device provides protection from a
faulted or shorted input. Without the protection, a
faulted or shorted input would discharge the battery
pack through the body diode of the internal pass
transistor.
6.1.1.5 Temperature Monitoring
The charge temperature window can be set by placing
fixed value resistors in series-parallel with a thermistor.
The resistance values of RT1 and RT2 can be calculated
with the following equations to set the temperature win-
dow of interest.
For NTC thermistors:
EQUATION 6-2:
PowerDissipation VDDMAX VPTHMIN
–IREGMAX
=
Where:
VDDMAX = the maximum input voltage
IREGMAX = the maximum fast charge current
VPTHMIN = the minimum transition threshold
voltage
PowerDissipation 5.5V 2.7V–550mA1.54W==
24kRT1
RT2 RCOLD
RT2 R+ COLD
----------------------------------+=
5kRT1
RT2 RHOT
RT2 R+ HOT
-------------------------------+=
Where:
RT1 = the fixed series resistance
RT2 = the fixed parallel resistance
RCOLD = the thermistor resistance at the
lower temperature of interest
RHOT = the thermistor resistance at the
upper temperature of interest
2008-2013 Microchip Technology Inc. DS20002090C-page 29
MCP73871
For example, by utilizing a 10 k at 25°C NTC
thermistor with a sensitivity index, , of 3892, the
charge temperature range can be set to 0-50°C by
placing a 1.54 k resistor in series (RT1), and a
69.8 k resistor in parallel (RT2) with the thermistor.
6.1.1.6 Charge Status Interface
A status output provides information on the state of
charge. The output can be used to illuminate external
LEDs or interface to a host microcontroller. Refer to
Table 5-1 for a summary of the state of the status
output during a charge cycle.
6.1.1.7 System Load Current
The preferred discharge current for Lithium-Ion cells
should always follow references and guidance from
battery manufacturers. The recommended system
load should be the lesser of 1.0 amperes or the
maximum discharge rate of the selected Lithium-Ion
cell. This limits the safety concerns of power
dissipation and exceeding the manufacturer’s
maximum discharge rate of the cell.
The ideal diode between VBAT and OUT is designed to
drive a maximum current up to 2A. The built-in thermal
shutdown protection may turn the MCP73871 device
off with high current.
6.2 PCB Layout Issues
For optimum voltage regulation, it is recommended to
place the battery pack closest to the device’s VBAT and
VSS pins to minimize voltage drops along the high
current-carrying PCB traces.
If the PCB layout is used as a heatsink, adding many
vias in the heatsink pad can help conduct more heat to
the PCB backplane, thus reducing the maximum junc-
tion temperature.
MCP73871
DS20002090C-page 30 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 31
MCP73871
7.0 PACKAGING INFORMATION
7.1 Package Marking Information
20-Lead QFN (4x4x0.9 mm) Example
Part Number * Marking Code
(Second Row) Part Number * Marking Code
(Second Row)
MCP73871-1AAI/ML 1AA MCP73871T-1AAI/ML 1AA
MCP73871-1CAI/ML 1CA MCP73871T-1CAI/ML 1CA
MCP73871-1CCI/ML 1CC MCP73871T-1CCI/ML 1CC
MCP73871-2AAI/ML 2AA MCP73871T-2AAI/ML 2AA
MCP73871-2CAI/ML 2CA MCP73871T-2CAI/ML 2CA
MCP73871-2CCI/ML 2CC MCP73871T-2CCI/ML 2CC
MCP73871-3CAI/ML 3CA MCP73871T-3CAI/ML 3CA
MCP73871-3CCI/ML 3CC MCP73871T-3CCI/ML 3CC
MCP73871-4CAI/ML 4CA MCP73871T-4CAI/ML 4CA
MCP73871-4CCI/ML 4CC MCP73871T-4CCI/ML 4CC
* Consult Factory for Alternative Device Options.
PIN 1 PIN 1
73871
1AA
I/ML^^
314256
3
e
Legend: XX...X Customer-specific information
Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
Pb-free JEDEC designator for Matte Tin (Sn)
*This package is Pb-free. The Pb-free JEDEC designator ( )
can be found on the outer packaging for this package.
Note: In the event the full Microchip part number cannot be marked on one line, it will be carried over
to the next line, thus limiting the number of available characters for customer-specific
information.
3
e
3
e
MCP73871
DS20002090C-page 32 2008-2013 Microchip Technology Inc.
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2008-2013 Microchip Technology Inc. DS20002090C-page 33
MCP73871
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MCP73871
DS20002090C-page 34 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 35
MCP73871
APPENDIX A: REVISION HISTORY
Revision C (September 2013)
The following is the list of modifications:
1. Updated Functional Block Diagram.
2. Added Table 4-1 in Section 4.0 “Device
Overview”.
3. Updated Section 7.0 “Packaging
Information”.
4. Minor grammatical and editorial corrections.
Revision B (May 2009)
The following is the list of modifications:
1. Updated the QFN-20 package drawing.
2. Updated Equation 4-1.
3. Updated Section 4.7 “Charge Termination”
and Equation 4-2.
4. Updated Equation 5-1.
Revision A (July 2008)
• Original Release of this Document.
MCP73871
DS20002090C-page 36 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 37
MCP73871
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
Device: MCP73871: USB/AC Battery Charger with PPM
MCP73871T: USB/AC Battery Charger with PPM
(Tape and Reel)
Output Options * * * Refer to table below for different operational options.
* * Consult Factory for Alternative Device Options.
Temperature: I = -40C to +85C
Package Type: ML = Plastic Quad Flat No Lead (QFN)
(4x4x0.9 mm Body), 20-lead
PART NO. XX
Output
Device
Options*
X/
Temp.
XX
Package
Examples: * *
a) MCP73871-1AAI/ML: 4.10V PPM Battery
Charger, 20LD QFN
pkg.
b) MCP73871-1CAI/ML: 4.10V, PPM Battery
Charger, 20LD QFN
pkg.
c) MCP73871-1CCI/ML: 4.10V, PPM Battery
Charger, 20LD QFN
pkg.
d) MCP73871-2AAI/ML: 4.20V, PPM Battery
Charger, 20LD QFN
pkg.
e) MCP73871-2CAI/ML: 4.20V PPM Battery
Charger, 20LD QFN
pkg.
f) MCP73871-2CCI/ML: 4.20V PPM Battery
Charger, 20LD QFN
pkg.
g) MCP73871-3CAI/ML: 4.35V PPM Battery
Charger, 20LD QFN
pkg.
h) MCP73871-3CCI/ML: 4.35V PPM Battery
Charger, 20LD QFN
pkg.
* * Consult Factory for Alternative Device Options
* Operational Output Options
Output
Options VREG
Safety Timer
Duration (Hours)
LBO Voltage
Threshold (V)
1AA 4.10V Disabled Disabled
1CA 4.10V 6 Disabled
1CC 4.10V 6 3.1
2AA 4.20V Disabled Disabled
2CA 4.20V 6 Disabled
2CC 4.20V 6 3.1
3CA 4.35V 6 Disabled
3CC 4.35V 6 3.1
4CA 4.40V 6 Disabled
4CC 4.40V 6 3.1
* * Consult Factory for Alternative Device Options.
MCP73871
DS20002090C-page 38 2008-2013 Microchip Technology Inc.
NOTES:
2008-2013 Microchip Technology Inc. DS20002090C-page 39
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING NOT LIMITED TO ITS CONDITION, QUALITY,
PERFORMANCE, MERCHANTABILITY OR FITNESS FOR
PURPOSE. Microchip disclaims all liability arising from this
information and its use. Use of Microchip devices in life support
and/or safety applications is entirely at the buyer’s risk, and the
buyer agrees to defend, indemnify and hold harmless Microchip
from any and all damages, claims, suits, or expenses resulting
from such use. No licenses are conveyed, implicitly or other-
wise, under any Microchip intellectual property rights.
Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
FlashFlex, KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro,
PICSTART, PIC32 logo, rfPIC, SST, SST Logo, SuperFlash
and UNI/O are registered trademarks of Microchip Technology
Incorporated in the U.S.A. and other countries.
FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MTP, SEEVAL and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of
Microchip Technology Inc. in other countries.
Analog-for-the-Digital Age, Application Maestro, BodyCom,
chipKIT, chipKIT logo, CodeGuard, dsPICDEM,
dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial
Programming, ICSP, Mindi, MiWi, MPASM, MPF, MPLAB
Certified logo, MPLIB, MPLINK, mTouch, Omniscient Code
Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,
PICtail, REAL ICE, rfLAB, Select Mode, SQI, Serial Quad I/O,
Total Endurance, TSHARC, UniWinDriver, WiperLock, ZENA
and Z-Scale are trademarks of Microchip Technology
Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
GestIC and ULPP are registered trademarks of Microchip
Technology Germany II GmbH & Co. KG, a subsidiary of
Microchip Technology Inc., in other countries.
All other trademarks mentioned herein are property of their
respective companies.
© 2008-2013, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
Printed on recycled paper.
ISBN: 978-1-62077-428-1
Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
DS20002090C-page 40 2008-2013 Microchip Technology Inc.
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08/20/13
