MICROCHIP MCP73871 Technical data

MCP73871

Stand-Alone System Load Sharing and Li-Ion / Li-Polymer

Battery Charge Management Controller

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 Cur rent 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’s also
capable of autonomous power source selection
between input or 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 supports 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. The constant voltage
regulation is fixed with four available options: 4.10V,

4.20V , 4.35V , or 4.40V to accommodate new , emerging
battery charging requirements. The MCP73871 device
also limits the charge current based on 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 allows 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.

© 2008 Microchip Technology Inc. DS22090A-page 1

MCP73871

2
3
4
511

12

13

14

PROG2

IN

STAT1 / LBO

PG

THERM

MCP73871

20-Lead QFN

STAT2

1 15

PROG1

6789 10

20 19 18 17 16

IN

OUT

OUT

CE

SEL

PROG3

TE

EXPOSED
PAD

V

BAT

V

BAT

VPCC

V

SS

V

SS

V

SS

V

BAT_SENSE

STAT1
LBO

IN OUT

P

G

V

BAT

Single-Cell
Li-Ion Battery

7

MCP73871 Typical Application

1, 20

8

18, 19

10 µF

10, 11, EP

Ac-dc Adapter
or
USB Port

STAT2

THERM

V

SS

PROG1

PROG3

12

13

R

PROG1

6

5

14, 15, 16

470Ω

470Ω

470Ω

2

4.7 µF

System
Load

SEL

T

E

PROG2

Hi

Low

Hi

Low

Hi

Low

3

4

9

R

PROG3

VPCC

NTC

10 kΩ

Hi

Low

17

CE

4.7 µF

Package Types

Typical Application Circuit

DS22090A-page 2 © 2008 Microchip Technology Inc.

MCP73871

STAT1

PROG1

V

BAT

G=0.001

V

SS

Direction

Control

TERM

+

-

+

-

LTVT

+

-

HTVT

THERM

50 µA

UVLO,
REFERENCE,
CHARGE
CONTROL,
TIMER,
AND
STATUS
LOGIC

STAT2

PG

Direction

Control

G=0.001

G=0.001

PROG2

IN

+

-

CURRENT
LIMIT

V

REF

G=0.001

+

-

CURRENT
LIMIT

V

REF

/2

PROG3

+

-

CA

V

REF

PRECONDITION

+

-

V

REF

+

-

VA

V

REF

V

REF

SEL

OUT

V

REF

TE

0.2Ω

0.2Ω

Ideal
Diode,
Synchronous
Switch

CHRG

+

-

V

REF

+

-

V

REF

VPCC

CE

V

BAT_SENSE

Functional Block Diagram

© 2008 Microchip Technology Inc. DS22090A-page 3

MCP73871

1.0 ELECTRICAL CHARACTERISTICS

† 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

Absolute Maximum Ratings†

VIN....................................................................................7.0V

All Inputs and Outputs w.r.t. ................V

(V

= VIN or V

DD

Maximum Junction Temperature, T

BAT

)

-0.3V to VDD+0.3V

SS

............Internally Limited

J

operational listings of this specification is not implied.
Exposure to maximum rating conditions for extended periods
may affect device reliability.

Storage temperature.....................................-65°C to +150°C

ESD protection on all pins

Human Body Model (1.5 kΩ in Series with 100pF)........≥ 4kV

Machine Model (200 pF, No Series Resistance).............300V

DC CHARACTERISTICS

Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = V

Typical values are at +25°C, V

IN

= [V

REG

(typical) + 1.0V]

Parameters Sym Min Typ Max Units Conditions

Supply Input

V

Supply Voltage V

Supply Current I

SS

IN

REG

+0.3V

— 2500 3750 µA Charging

—6V

— 260 350 µA Charge Complete
— 180 300 µA Standby
— 28 50 µA Shutdown

V

+

–

V

REG

0.15V

V

REG

0.07V

UVLO Start Threshold V

UVLO Stop Threshold V

UVLO Hysteresis V

START

STOP

HYS

REG

0.05V

V

REG

0.07V
—90—mV

Voltage Regulation (Constant Voltage Mode)

Regulated Charge Voltage V

REG

4.080 4.10 4.121 V VDD=[V

4.179 4.20 4.221 V I

4.328 4.35 4.372 V T

4.378 4.40 4.422

Regulated Charge Voltage Tolerance V

RTOL

-0.5 — +0.5 % TA= +25°C

-0.75 — +0.75 % T

Line Regulation |(ΔV

Load Regulation |ΔV

BAT/VBAT

ΔV

BAT/VBAT

)/

— 0.08 0.20 %/V V

|

DD

| — 0.08 0.18 % I

Supply Ripple Attenuation PSRR — -47 — dB I

—-40—dBI

Current Regulation (Fast Charge Constant-Current Mode)

AC-Adapter Fast Charge Current I

REG

90 100 110 mA PROG1 = 10 kΩ

900 1000 1100 mA PROG1 = 1kΩ,

USB Fast Charge Current I

REG

80 90 100 mA PROG2 = Low, SEL = Low,

400 450 500 mA PROG2 = High, SEL = Low,

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.

+ 0.3V to 6V, TA = -40°C to +85°C.

REG

+

V

+

REG

VVDD= Low to High

0.25V

+

V

+

REG

0.17V

VVDD= High to Low

< V

(V

DD

V

< V

DD

OUT

=-5°C to +55°C

A

= -5°C to +55°C

A

=[V

DD

I

OUT
OUT

V

= [V

DD
OUT
OUT

=-5°C to +55°C, SEL = Hi

T

A

- 100 mV or

BAT

)

STOP

(typical)+1V]

REG

=10 mA

(typical)+1V] to 6V

REG

=10 mA
=10 mA to 150 mA

(typical)+1V]

REG

=10mA, 1kHz
=10 mA, 10 kHz

(Note 2)

(Note 2)

= -5°C to +55°C

T

A

DS22090A-page 4 © 2008 Microchip Technology Inc.

DC CHARACTERISTICS (CONTINUED)

Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = V

Typical values are at +25°C, V

IN

= [V

REG

(typical) + 1.0V]

Parameters Sym Min Typ Max Units Conditions

Input Current Limit Control (ICLC)

USB-Port Supply Current Limit I

LIMIT_USB

80 90 100 mA PROG2 = Low, SEL = Low

400 450 500 mA PROG2 = High, SEL = Low

AC-DC Adapter Current Limit I

LIMIT_AC

1500 1650 1800 mA SEL = High, TA=-5°C to +55°C

Voltage Proportional Charge Control (VPCC - Input Voltage Regulation)

VPCC Input Threshold V
VPCC Input Threshold Tolerance V
Input Leakage Current I

VPCC
RTOL

LK

—1.23—VI

-3 — +3 % TA=-5°C to +55°C

—0.011µAV

Precondition Current Regulation (Trickle Charge Constant-Current Mode)

Precondition Current Ratio I

Precondition Current Threshold Ratio V

PREG

PTH

Precondition Hysteresis V

/ I

/ V

PHYS

REG

REG

7.5 10 12.5 % PROG1 = 1.0 kΩ to 10 kΩ

69 72 75 % V
— 105 — mV V

Automatic Charge Termination Set Point

Charge Termination Current Ratio I

TERM

75 100 125 mA PROG3 = 10 kΩ

7.5 10 12.5 mA PROG3 = 100 kΩ

Automatic Recharge

V

-

Recharge Voltage Threshold Ratio V

RTH

REG

0.21V

V

0.15V

IN-to-OUT Pass Transistor ON-Resistance

ON-Resistance R

DS_ON

— 200 — mΩ VDD = 4.5V, TJ = 105°C

Charge Transistor ON-Resistance

ON-Resistance R

DSON_

— 200 — mΩ VDD = 4.5V, TJ = 105°C

Ideal Diode ON-Resistance

ON-Resistance R
Diode Forward Voltage Drop V

DS_ON

FWD

— 200 — mΩ VDD = 4.5V, TJ = 105°C
— 0.7 1 V Switch Off (Note 1)

Battery Discharge Current

Output Reverse Leakage Current I

DISCHARGE

— 30 40 µA Shutdown

— 30 40 µA Shutdown (0 < V
—3040µAV
— -6 -13 µA Charge Complete

Status Indicators - STAT1 ( LBO

Sink Current I
Low Output Voltage V
Input Leakage Current I

Low Battery Indicator (LBO

Low Battery Detection Threshold V

), STAT2, PG

)

SINK

OL

LK

LBO

—1635mA
—0.41VI
— 0.01 1 µA High Impedance, VDD on pin

— Disable — V

2.85 3.0 3.15 V T

2.95 3.1 3.25 V

3.05 3.2 3.35 V

Low Battery Detection Hysteresis V

LBO_HYS

— 150 — mV V

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.

REG

REG

-

MCP73871

+ 0.3V to 6V, TA = -40°C to +85°C.

=-5°C to +55°C

T

A

=10 mA

OUT

= V

V

REG

0.09V

-

VPCC

T

A

BAT
BAT

T

A

VV

BAT

(V

BAT

SINK

BAT

A

BAT

DD

=-5°C to +55°C

Low to High
High to Low

=-5°C to +55°C

High to Low

< VDD < V

BAT

= Power Out, No Load

= 4 mA

> VIN, PG = Hi-Z

=-5°C to +55°C

Low to High

UVLO

DD

< V

)

)

BAT

© 2008 Microchip Technology Inc. DS22090A-page 5

MCP73871

DC CHARACTERISTICS (CONTINUED)

Electrical Specifications: Unless otherwise indicated, all limits apply for VIN = V

Typical values are at +25°C, V

IN

= [V

REG

(typical) + 1.0V]

Parameters Sym Min Typ Max Units Conditions

PROG1 Input (PROG1)

Charge Impedance Range R

PROG

1—20kΩ

PROG3 Input (PROG3)

Termination Impedance Range R

PROG

5 — 100 kΩ

PROG2 Input (PROG2)

Input High Voltage Level V
Input Low Voltage Level V
Input Leakage Current I

IH
IL

LK

1.8 — — V
——0.8V
—0.011µAV

Timer Enable (TE)

Input High Voltage Level V
Input Low Voltage Level V
Input Leakage Current I

IH
IL

LK

1.8 — — V Note 1
——0.8VNote 1
—0.011µAV

Chip Enable (CE)

Input High Voltage Level V
Input Low Voltage Level V
Input Leakage Current I

IH
IL

LK

1.8 — — V
——0.8V
—0.011µAVCE = V

Input Source Selection (SEL)

Input High Voltage Level V
Input Low Voltage Level V
Input Leakage Current I

IH
IL

LK

1.8 — — V
——0.8V
—0.011µAV

Thermistor Bias

Thermistor Current Source I

THERM

47 50 53 µA 2 kΩ < R

Thermistor Comparator

Upper Trip Threshold V
Upper Trip Point Hysteresis V
Lower Trip Threshold V
Lower Trip Point Hysteresis V

T1

T1HYS

T2

T2HYS

1.20 1.24 1.26 V VT1 Low to High
—-40—mV

0.23 0.25 0.27 V VT2 High to Low
—40—mV

Thermal Shutdown

Die Temperature T
Die Temperature Hysteresis T

SD

SDHYS

— 150 — °C
—10—°C

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.

REG

+ 0.3V to 6V, TA = -40°C to +85°C.

= V

PROG2

TE

SEL

= V

= V

DD

DD

DD

THERM

DD

< 50 kΩ

DS22090A-page 6 © 2008 Microchip Technology Inc.

AC CHARACTERISTICS

Electrical Specifications: Unless otherwise indicated, all limits apply for V

Typical values are at +25°C, V

DD

= [V

(typical) + 1.0V]

REG

Parameters Sym Min Typ Max Units Conditions

UVLO Start Delay t

START

—— 5 msVDD Low to High

Current Regulation

Transition Time Out of Precondition t
Current Rise Time Out of Precondition t
Precondition Comparator Filter Time t
Termination Comparator Filter Time t

Comparator Filter Time t

Charge
Thermistor Comparator Filter Time t

DELAY

RISE

PRECON

TERM

CHARGE

THERM

——10 msV
——10 msI

0.4 1.3 3.2 ms Average V

0.4 1.3 3.2 ms Average I

0.4 1.3 3.2 ms Average V

0.4 1.3 3.2 ms Average THERM Rise/Fall

Elapsed Timer

Elapsed Timer Period t

ELAPSED

— 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 t
Status Output Turn-on t

OFF

ON

— — 500 µs I
— — 500 µs I

Note 1: Internal safety timer is tested base on internal oscillator frequency measurement.

= 4.6V to 6V.

IN

MCP73871

< V

to V

BAT

PTH

Rising to 90% of I

OUT

BAT

OUT

BAT

= 1 mA to 0 mA

SINK

= 0 mA to 1 mA

SINK

BAT

Rise/Fall

Falling

Falling

> V

PTH

REG

TEMPERATURE SPECIFICATIONS

Electrical Specifications: Unless otherwise indicated, all limits apply for V

Typical values are at +25°C, V

Parameters Sym Min Typ Max Units Conditions

Temperature Ranges

Specified Temperature Range T
Operating Temperature Range T
Storage Temperature Range T

Thermal Package Resistances

Thermal Resistance, 20LD-QFN, 4x4 θ

DD

= [V

(typical) + 1.0V]

REG

A
J
A

JA

-40 — +85 °C

-40 — +125 °C

-65 — +150 °C

— 35 — °C/W 4-Layer JC51-7 Standard Board,

= 4.6V to 6V.

IN

Natural Convection

© 2008 Microchip Technology Inc. DS22090A-page 7

MCP73871

4.176

4.184

4.192

4.200

4.208

4.216

4.224

4.232

4.240

4.6 4.9 5.1 5.4 5.6 5.9

Supply Volta ge (V)

Battery Regulation Voltage (V)

Temperature = +25°C

I

OUT

= 100 mA

I

OUT

= 500 mA

I

OUT

= 900 mA

I

OUT

= 10 mA

4.190

4.198

4.206

4.214

4.222

4.230

4.238

-45 -30 -15 0 15 30 45 60 75 90

Ambient Temperature (°C)

Battery Regulation Voltage (V)

I

OUT

= 10 mA

I

OUT

= 100 mA

I

OUT

= 500 mA

I

OUT

= 1000 mA

0

100

200

300

400

500

600

700

800

900

1000

1234567891011121314151617181920

R

PROG

(kΩ)

I

REG

(mA)

V

DD

Temperature = +25°C

4.100

4.120

4.140

4.160

4.180

4.200

4.220

4.240

4.260

4.280

4.300

0

100

200

300

400

500

600

700

800

900

1000

Charge Current (mA)

(V)

Temperature = +25°C

V

DD

10.0

15.0

20.0

25.0

30.0

35.0

40.0

-45 -30 -15 0 15 30 45 60 75 90
Temperature (°C)

(µA)

V

BAT

= 4.2V

V

DD

= Floating

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

3.0 3.2 3.4 3.6 3.8 4.0 4.2
Battery Voltage (V)

(µA)

VDD= V

BAT

Temperature = +25°C

2.0 TYPICAL PERFORMANCE CURVES

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.

Note: Unless otherwise indicated, VIN = [V

(typical) + 1V], I

REG

FIGURE 2-1: Battery Regulation Voltage
(V

) vs. Supply Voltage (VDD).

BAT

= 10 mA and TA= +25°C, Constant-voltage mode.

OUT

Battery Regulation Voltage

FIGURE 2-4: Charge Current (I
Battery Regulation Voltage (V

BAT

OUT

).

= 5.2V

) vs.

FIGURE 2-2: Battery Regulation Voltage

) vs. Ambient Temperature (TA).

(V

BAT

FIGURE 2-3: Charge Current (I
Programming Resistor (R

DS22090A-page 8 © 2008 Microchip Technology Inc.

Battery Discharge Current

FIGURE 2-5: Output Leakage Current
(I

DISCHARGE

= 5.2V

Battery Discharge Current

PROG

).

OUT

) vs.

FIGURE 2-6: Output Leakage Current
(I

DISCHARGE

(V

BAT

) vs. Ambient Temperature (TA).

) vs. Battery Regulation Voltage

).

MCP73871

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

3.03.23.43.63.84.04.2
Battery Voltage (V)

(µA)

VDD= Floating
Temperat ure = +25° C

800

830

860

890

920

950

980

1010

1040

1070

1100

1130

1160

1190

4.5 4.8 5.0 5.3 5. 5 5.8 6.0
Supply Voltage (V)

I

REG

(mA)

R

PROG

= 1 kΩ

Temperature = +25°C

450

460

470

480

490

500

510

520

530

540

550

4.5 4.8 5.0 5 .3 5.5 5.8 6.0
Supply Voltage (V)

I

REG

(mA)

PROG

= 2 kΩ

T

90

92

94

96

98

100

102

104

106

108

110

4.54.8 5.05.35.55.86.0
Supply Voltage (V)

I

REG

(mA)

R

PROG

= 10 kΩ

Temp eratu re = +2 5°C

700

740

780

820

860

900

940

980

1020

1060

1100

-45 -30 -15 0 15 30 45 60 75 90

Ambient Temperature (°C)

Charge Current (mA)

R

PROG

V

DD

V

90

92

94

96

98

100

102

104

106

108

110

-45 -30 -15 0 15 30 45 60 75 90

Ambient Temperature (°C)

Charge Current (mA)

R

PROG

= 10 kΩ

V

DD

Note: Unless otherwise indicated, VIN = [V

Battery Discharge Current

(typical) + 1V], I

REG

FIGURE 2-7: Output Leakage Current
(I

DISCHARGE

) vs. Battery Voltage (V

BAT

).

= 10 mA and TA= +25°C, Constant-voltage mode.

OUT

FIGURE 2-10: Charge Current (I
Supply Voltage (V

DD

).

OUT

) vs.

FIGURE 2-8: Charge Current (I
Supply Voltage (V

R

emperat ure = +25°C

DD

).

FIGURE 2-9: Charge Current (I
Supply Voltage (V

DD

).

OUT

OUT

) vs.

) vs.

FIGURE 2-11: Charge Current (I
Ambient Temperature (T

).

A

FIGURE 2-12: Charge Current (I
Ambient Temperature (T

).

A

= 1 kΩ

= 5.2

OUT

OUT

) vs.

= 5.2V

) vs.

© 2008 Microchip Technology Inc. DS22090A-page 9

MCP73871

41

43

45

47

49

51

53

55

-45 -30 -15 0 15 30 45 60 75 90
Ambient Temperature (°C)

Charge Current (mA)

R

PROG

= 20 kΩ

V

DD

= 5.2V

0

200

400

600

800

1000

1200

25 50 75 100 125 150

Ambient Temperature (°C)

Charge Current (mA)

VDD = 5.2V
R

PROG

= 1 kΩ

0

100

200

300

400

500

600

25 50 75 100 125 150

Ambient Temperature (°C)

Charge Current (mA)

VDD = 5.2V
R

PROG

= 2 kΩ

0

20

40

60

80

100

120

25 50 75 100 125 150

Ambient Temperature (°C)

Charge Current (mA)

VDD = 5.2V
R

PROG

= 10 kΩ

47.0

47.5

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

4.6 4.8 5.0 5 .2 5.4 5.6 5.8 6.0

Supply Voltage (V)

Thermistor Current (µA)

Temperature = +25°C

47.0

47.5

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

-45 -30 -15 0 15 30 45 60 75 90
Ambient Temperature (°C)

Thermistor Current (µA)

VDD = 5.2V

Note: Unless otherwise indicated, VIN = [V

FIGURE 2-13: Charge Current (I
Ambient Temperature (T

).

A

(typical) + 1V], I

REG

) vs.

OUT

= 10 mA and TA= +25°C, Constant-voltage mode.

OUT

FIGURE 2-16: Charge Current (I
Junction Temperature (T

).

J

OUT

) vs.

FIGURE 2-14: Charge Current (I
Junction Temperature (T

FIGURE 2-15: Charge Current (I
Junction Temperature (T

DS22090A-page 10 © 2008 Microchip Technology Inc.

) vs.

).

J

).

J

OUT

OUT

) vs.

FIGURE 2-17: Thermistor Current (I
vs. Supply Voltage (V

DD

).

FIGURE 2-18: Thermistor Current (I
vs. Ambient Temperature (T

).

A

THERM

THERM

)

)

MCP73871

-60

-50

-40

-30

-20

-10

0

0.01 0 .1 1 10 100 1000

Frequency (kHz)

PSRR (dB)

I

OUT

= 10 mA

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

-0.0008 -0.0006 -0.0004 -0.0002 0 0.0002
Time (s)

Output Voltage (V)

-0.7

-0.5

-0.3

-0.1

0.1

0.3

Output Current (A)

I

OUT

= 100 mA

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

-0.0008 -0.0006 -0.0004 -0.0002 0 0.0002

Time (s)

Output Voltage (V)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Output Current (A)

I

OUT

= 500 mA

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

-0.001 0 0.001 0.002 0.003 0.004
Time (s)

Output Current (A)

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

Output Ripple (V)

I

OUT

= 100 mA

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0

.

0

0

0

7

5

0

.

0

0

1

1

5

0

.

0

0

1

5

5

0

.

0

0

1

9

5

0

.

0

0

2

3

5

0

.

0

0

2

7

5

Time (s)

Output Current (A)

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

Output Ripple (V)

I

OUT

= 500 mA

Input Voltage (V)

Time (ms)

Note: Unless otherwise indicated, VIN = [V

REG

FIGURE 2-19: Power Supply Ripple Rejection (PSRR).

(typical) + 1V], I

= 10 mA and TA= +25°C, Constant-voltage mode.

OUT

FIGURE 2-22: Load Transient Response.
I

= 100 mA.

OUT

FIGURE 2-20: Line Transient Response.
I

= 100 mA.

OUT

FIGURE 2-21: Line Transient Response.

= 500 mA.

I

OUT

© 2008 Microchip Technology Inc. DS22090A-page 11

FIGURE 2-23: Load Transient Response.

= 500 mA.

I

OUT

UVLO (V)

FIGURE 2-24: Undervoltage Lockout.

MCP73871

Input Voltage (V)

Time (ms)

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.10.20.30.40.5

Time (Minutes)

Charge Voltage (V)

0

0.1

0.2

0.3

0.4

0.5

Charge Current (A)

MCP73871
V

DD

= 5.2V
SEL = Low
PROG2 = Low

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1020304050607080

Time (Minute)

Charge Voltage (V)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Charge Current (A)

MCP73871
V

DD

= 5.2V

R

PROG1

= 1 kȍ

R

PROG3

= 25 kȍ

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.2 0.4 0.6 0.8 1

Time (Minute)

Charge Voltage (V)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Charge Current (A)

Preconditioning

Preconditioning Threshold Voltage

Fast Charge (Constant Current)

MCP73871
V

DD

= 5.2V

R

PROG1

= 1 kȍ

R

PROG3

= 25 kȍ

Note: Unless otherwise indicated, VIN = [V

FIGURE 2-25: Startup Delay.

(typical) + 1V], I

REG

Startup Voltage (V)

= 10 mA and TA= +25°C, Constant-voltage mode.

OUT

FIGURE 2-27: Complete Charge Cycle (1000 mAh Li-Ion Battery).

FIGURE 2-26: Complete Charge Cycle (130 mAh Li-Ion Battery).

DS22090A-page 12 © 2008 Microchip Technology Inc.

FIGURE 2-28: Typical Charge Profile in Preconditioning (1000 mAh Battery).

3.0 PIN DESCRIPTION

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1: PIN FUNCTION TABLES

MCP73871

Pin

Number

1, 20 OUT O System Output Terminal

2 VPCC I Voltage proportional charge control
3 SEL I Inpu t type selection (Low for USB port, High for ac-dc adapter)
4 PROG2 I USB port input current limit selection when SEL = Low.

5 THERM I/O Thermistor monitoring input and bias current
6PG
7 STAT2 O Charge Status Output 2 (Open-Drain)
8STAT1 /

9TEI Timer Enable; Enables Safety Timer when active Low

10, 11, EP V

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

14, 15 V

16 V
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: The input pins should always tie to either High or Low, and never allow floating to ensure operation properly .

Symbol I/O Function

(Low = 100 mA, High = 500 mA)

O Power-Good Status Output (Open-Drain)

O Charge Status Output 1 (Open-Drain). Low battery output indicator when

LBO

SS

BAT

BAT_SENSE

V

BAT>VIN

— 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 V
Board (PCB)

for both USB port and ac-dc adapter.
I/O Battery Positive Input and Output connection
I/O Battery Voltage Sense

pin on the Printed Circuit

SS

3.1 Power Supply Input (IN)

A supply voltage of V
recommended. Bypass to V

4.7 µF.

+ 0.3V to 6V is

REG

with a minimum of

SS

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, allows for proper charge termination and
the system to run with an absent or defective battery
pack. Also, this feature gives the system priority on
input power, allowing the system to power-up with
deeply depleted battery packs. Bypass to V
minimum of 4.7 µF is recommended.

© 2008 Microchip Technology Inc. DS22090A-page 13

with a

SS

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. Further demand from the system is supported
by the battery, if possible. To active this feature, simply
supply 1.23V or greater to 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.

MCP73871

V

VPCC

R

2

R1R2+

-------------------

⎝⎠

⎛⎞

V

IN

1.23V=

×

=

1.23V

110k

Ω

110kΩR1+

----------------------------- -

⎝⎠

⎛⎞

5V

×

=

R

1

337.2kΩ=

330 kΩ

110 kΩ

V

IN

VPCC

The voltage divider equation is shown below:

The calculated R
selected for R2. The 330 kΩ resistor is selected for R
to build the voltage divider for VPCC.

equals to 337.2 kΩ when 110 kΩ is

1

FIGURE 3-1: Voltage Divider Example.

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 input source type and system load require­ment.

1

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 1 unit load input current from USB port
(100 mA); a logic High selects a 5 unit loads input cur­rent from 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.

3.4 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 designed to provide a typical 1.65A to system
power and charge Li-Ion battery from a regular 5V wall
adapter. 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
(V

)

SS

Connect to negative terminal of battery, system load
and input supply.

3.6 Battery Charge Control Output

)

(V

BAT

Connect to positive terminal of Li-Ion / Li-Polymer
batteries. Bypass to V
ensure loop stability when the battery is disconnected.

with a minimum of 4.7 µF to

SS

3.7 Battery Voltage Sense
(V

BAT_SENSE

Connect to positive terminal of battery. A precision
internal voltage sense regulates the final voltage on
this pin to V

DS22090A-page 14 © 2008 Microchip Technology Inc.

.

REG

)

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
user via an illuminated LED or to the system via a pull­up resistor for interfacing to a host microcontroller that
an input source other than the battery is supplying
power. Refer to Table 5-1 for a summary of the status
output during a charge cycle.

output can be used as an indication to the

3.13 Low Battery Output (LBO)

STAT1 also serves as low battery output (LBO) if the
selected MCP73871 is equipped with this feature. It
reminds the system or end user when the Li-Ion battery
voltage level is low. The LBO
system is running from the Li-Ion batteries. The LBO
indicator can be used as an indication to the user via lit
up LED or to the system via a pull-up resistor for inter­facing to a host microcontroller that an input source
other than the battery is supplying power. Refer to

Table 5-1 for a summary of the status output during a

charge cycle.

feature enables when the

3.14 Timer Enable (TE)

The timer enable (TE) feature 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
when the system load is substantially limiting the
available supply current to charge the battery. The TE
input is compatible with 1.8V logic.

Note: The built-in safety timer is available for the

input can be used to disable the timer

following options: 4 HR, 6 HR and 8 HR.

3.15 Battery Temperature Monitor (THERM)

The MCP73871 device continuously monitor battery
temperature during a charge cycle by measuring the
voltage between the THERM and V
50 µA current source provides the bias for most
common 10 kΩ negative-temperature coefficient
thermistors (NTC). 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.

pins. An internal

SS

3.16 Charge Enable (CE)

With the CE input Low, the Li-Ion battery charger
feature of the MCP73871 will be disabled. The charger
feature 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.

MCP73871

© 2008 Microchip Technology Inc. DS22090A-page 15

MCP73871

SHUTDOWN MODE *

V

DD

< V

UVLO

VDD < V

BAT

STAT1 = Hi-Z
STAT2 = Hi-Z

PG = Hi-Z

PRECONDITIONING MODE

Charge Current = I

PREG

STAT1 = LOW

STAT2 = Hi-Z

PG = LOW

Tim er Reset

CONSTANT VOLTAGE MODE

Charge Voltage = V

REG

STAT1 = LOW

PG = LOW

V

BAT

> V

PTH

CHARGE COMPLETE MODE

No Charge Current

STAT1 = Hi-Z

STAT2 = LOW

PG = LOW

Timer Reset

I

BAT

< I

TERM

Tim er Expired

V

BAT

< V

PTH

STANDBY MODE *

V

BAT

> (V

REG

+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 *

V

IN

< V

BAT

STAT1 = LOW

STAT2 = Hi-Z

PG = Hi-Z

V

BAT

> V

PTH

STAT2 = Hi-Z

Tim er Reset

FAST CHARGE MODE

Charge Current = I

REG

STAT1 = LOW

STAT2 = Hi-Z

PG = LOW

Timer Enabled

4.0 DEVICE OVERVIEW

The MCP73871 device is a simple, but fully integrated
linear charge management controllers with system
load sharing feature. Figure 4-1 depicts the opera­tional flow algorithm.

FIGURE 4-1: MCP73871 Device Flow Char t.

DS22090A-page 16 © 2008 Microchip Technology Inc.

MCP73871

0.2Ω

Ideal
Diode,
Synchronous
Switch

Direction

Control

0.2Ω

Current

Limit

Direction

Control

Charge
FET

System
Power
FET

V

BAT

IN OUT

Charge
Control

I

REG

1000V

R

PROG

---------------- -=

Where:

R

PROG

= kilo-ohms (kΩ)

I

REG

= milliampere (mA)

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 become operational.

The UVLO circuit places the device in shutdown mode
if the input supply falls to 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 approxi­mately 100 mV of the voltage at the V

pin, the

BAT

MCP73871 device is placed in a shutdown mode.
During any UVLO condition, the battery reverse

discharge current shall be less than 2 µA.

4.2 SYSTEM LOAD SHARING

The system load sharing feature gives the system
priority on input power, allowing the system to power­up 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).

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 V

when SEL = High.

SS

When SEL = Low, PROG2 needs to tie to High or Low
for proper operation.

4.4 PRECONDITIONING

If the voltage at the V
tioning threshold, the MCP73871 device enters a pre­conditioning mode. The preconditioning threshold is
factory set. Refer to Section 1.0 “Electrical Charac-
teristics” 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 V
preconditioning threshold, the MCP73871 device
enters the constant current (fast charge) mode.

pin is less than the precondi-

BAT

BAT pin rises above the

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 V
charge current are calculated using the following
equation:

EQUATION 4-1:

. The program resistor and the

SS

FIGURE 4-2: System Load Sharing Diagram.

© 2008 Microchip Technology Inc. DS22090A-page 17

Constant current mode is maintained until the voltage
at the V

pin reaches the regulation voltage, V

BAT

REG

.

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 Stand-by mode where it remains until a battery is
reinserted.

MCP73871

0

200

400

600

800

1000

1200

25 50 75 100 125 150

Ambient Temperature (°C)

Charge Current (mA)

VDD = 5.2V
R

PROG

= 1 kΩ

4.6 CONSTANT VOLTAGE MODE

When the voltage at the V
regulation voltage, V

, constant voltage regulation

REG

begins. The regulation voltage is factory set to 4.10V
or 4.20V with a tolerance of ±0.5%.

pin reaches the

BAT

4.7 CHARGE TERMINATION

The charge cycle is terminated when, during constant
voltage mode, the average charge current diminishes
below a threshold established with the value of a
resistor connected from PROG3 to V

or internal timer

SS

has expired. 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 charge current is latched off and the MCP73871
device enters a charge complete mode.

4.8 AUTOMATIC RECHARGE

The MCP73871 device continuously monitors the volt­age at the V
voltage drops below the recharge threshold, another
charge cycle begins and current is once again supplied
to the battery or load. The recharge threshold is factory
set. Refer to Section 1.0 “Electrical Characteristics”
for recharge threshold options.

Note: Charge termination and automatic

pin in the charge complete mode. If the

BAT

recharge features avoid constant charging
Li-Ion batteries to prolong life of Li-Ion
batteries while keeping their capacity at
healthy level.

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 “Electri-
cal 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 will resume 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 monitor battery
temperature during a charge cycle by measuring the
voltage between the THERM and V
50 µA current source provides the bias for most
common 10 kΩ negative-temperature coefficient
thermistors (NTC). 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 charge pass transistor and holding the
timer value. The charge cycle resumes when the
voltage at the THERM pin returns to the normal range.

pins. An internal

SS

DS22090A-page 18 © 2008 Microchip Technology Inc.

MCP73871

-200

-100

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600 700

Load Curr ent (mA)

Current (mA)

Input Current
Battery C urrent
Load Curr ent

Ideal
Diod e

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, then the battery charging current is
reduced. The VPCC control tries to reach a steady­state 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 will become
forward biased and the battery is able to 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 input ICLC is
reached, the ideal diode will become forward bia sed
and the battery is able to 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.

© 2008 Microchip Technology Inc. DS22090A-page 19

FIGURE 4-4: Input Current Limit Control ­USB Port.

MCP73871

I

REG

1000V

R

PROG

---------------- -=

Where:

R

PROG

= kilo-ohms (kΩ)

I

REG

= milliampere (mA)

5.0 DETAILED DESCRIPTION

1.24V and 0.25V, typically. Once a voltage outside the
thresholds is detected during a charge cycle, the

5.1 Analog Circuitry

5.1.1 LOAD SHARING AND LI-ION
BATTERY MANAGEMENT INPUT
SUPPLY (V

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 (V

)

IN

) with SEL

USB

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 kΩ resistor from THERM to V

SS

pin. The MCP73871 device automatically powers the
system with the Li-Ion battery when the V

input is not

IN

5.2 Digital Circuitry

present.

5.2.1 STATUS INDICATORS AND POWER-

5.1.2 FAST CHARGE CURRENT
REGULATION SET (PROG1)

For the MCP73871 device, the charge curre nt regula­tion can be scaled by placing a programming resistor
(R

) from the PROG1 pin to VSS. The program

PROG1

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) to the fast charge
current.

5.1.3 BATTERY CHARGE CONTROL
OUTPUT (V

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.

BAT

)

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 V
50 µA current source provides the bias for most
common 10 kΩ negative-temperature coefficient
(NTC) or positive-temperature coefficient (PTC)
thermistors.The current source is controlled, avoiding
measurement sensitivity to fluctuations in the supply
voltage (V
voltage at the THERM pin to factory set thresholds of

DS22090A-page 20 © 2008 Microchip Technology Inc.

). The MCP73871 device compares the

DD

pins. An internal

SS

The charge status outputs have two different states:
Low (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

CHARGE CYCLE STATE STAT1 STAT2 PG

Shutdown (VDD = V
Shutdown (V
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

5.2.2 AC-DC ADAPTER AND USB PORT

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 selecting 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 V

GOOD (P

= IN) Hi-Z Hi-Z L

DD

G)

) Hi-Z Hi-Z Hi-Z

BAT

POWER SOURCE REGULATION
SELECT (SEL)

when driving SEL High.

SS

MCP73871

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. However, there is a diode path back to the
input, and as such, the output should only be pulled up
to the input. The PG
to the MCP73871 device is above the UVLO threshold
and greater than the battery voltage. The PG
can be used as an indication to the system that an input
source other than the battery is supplying power.

output is low whenever the input

output

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
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.

input can be used to disable

© 2008 Microchip Technology Inc. DS22090A-page 21

MCP73871

STAT1
LBO

IN OUT

P

G

V

BAT

Single-Cell
Li-Ion Battery

7

MCP73871 Device Typical Application

1, 20

8

18, 19

10 µF

10, 11, EP

5V AC-DC Adapter

or

USB Port

STAT2

THERM

V

SS

PROG1

PROG3

12

13

R

PROG1

6

5

14, 15, 16

470Ω

470Ω

470Ω

2

4.7 µF

System
Load

SEL

T

E

PROG2

Hi

Low

Hi

Low

Hi

Low

3

4

9

R

PROG3

VPCC

NTC

10 kΩ

Hi

Low

17

CE

4.7 µF

330 kΩ

110 kΩ

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1020304050607080

Time (Minute)

Charge Voltage (V)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Charge Current (A)

MCP73871
V

DD

= 5.2V

R

PROG1

= 1 kȍ

R

PROG3

= 25 kȍ

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.2 0.4 0.6 0.8 1

Time (Minute)

Charge Voltage (V)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Charge Current (A)

Preconditioning

Preconditioning Threshold Voltage

Fast Charge (Constant Current)

MCP73871
V

DD

= 5.2V

R

PROG1

= 1 kȍ

R

PROG3

= 25 kȍ

6.0 APPLICATIONS

The MCP73871 device is designed to operate in
conjunction with a host microcontroller or in stand­alone applications. The MCP73871 device provides
the preferred charge algorithm for Lithium-Ion and

Lithium-Polymer cells Constant-current followed by
Constant-voltage. Figure 6-1 depicts a typical stand­alone MCP73871 application circuit, while Figures 6-

2 and 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).

DS22090A-page 22 © 2008 Microchip Technology Inc.

FIGURE 6-3: Typical Charge Profile in Preconditioning (1000 mAh Battery).

MCP73871

PowerDissipation V

DDMAXVPTHMIN

–()I

REGMAX

×=

Where:

V

DDMAX

= the maximum input voltage

I

REGMAX

= the maximum fast charge current

V

PTHMIN

= the minimum transition threshold

voltage

PowerDissipation 5.5V 2.7V–()550mA× 1.54W==

24k

Ω

R

T1

RT2R

COLD

×

R

T2

R+

COLD

-------------------------------- -+=

5k

Ω

R

T1

RT2R

HOT

×

R

T2

R+

HOT

---------------------------- -+=

Where:

R

T1

= the fixed series resistance

R

T2

= the fixed parallel resistance

R

COLD

= the thermistor resistance at the

lower temperature of interest

R

HOT

= the thermistor resistance at the

upper temperature of interest

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:

This power dissipation with the battery charger in the
QFN-20 package will cause thermal regulation to be
entered 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. In order to maintain good AC stability in
the Constant Volt age mode, a minimum capacitance of

4.7 µF is recommended to bypass the V

pin to VSS.

BAT

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 byp ass cap aci­tance may be necessary to compensate for the
inductive nature of the battery pack.

Virtually any good quality output filter capacitor can be
used, independent 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 a 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 R
with the following equations in order to set the
temperature window of interest.

For NTC thermistors:

and RT2 can be calculated

T1

For example, power dissipation with a 5V, ±10% input
voltage source and 500 mA, ±10% fast charge current
is:

EXAMPLE 6-1:

© 2008 Microchip Technology Inc. DS22090A-page 23

EQUATION 6-2:

MCP73871

For example, by utilizing a 10 kΩ at 25°C NTC
thermistor with a sensitivity index, β, of 3892, the
charge temperature range can be set to 0°C - 50°C by
placing a 1.54 kΩ resistor in series (R

69.8 kΩ resistor in parallel (RT2) with the thermistor.

), and a

T1

6.1.1.6 Charge Status Interface

A status output provides information on the state of
charge. The output can be used to illuminate externa l
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. Due to the safety concerns
when using Lithium-Ion batteries and power dissipa­tion of linear solutions, the system load when design
with the MCP73871 device is recommended to be less
than 1A or the maximum discharge rate of the
selected Lithium-Ion cell. Whichever is smaller is
recommended.

The idea diode between V
drive a maximum current up to 2A. The built-in thermal
shutdown protection may turn the MCP73871 device
off with high current.

and OUT is designed to

BAT

6.2 PCB Layout Issues

For optimum voltage regulation, place the battery pack
as close as possible to the device’s V
recommended 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 backplane of the PCB, thus reducing the maximum
junction temperature.

and VSS pins,

BAT

DS22090A-page 24 © 2008 Microchip Technology Inc.

7.0 PACKAGING

20-Lead QFN Example:

XXXXXX
XXXXXX

YWWNNN

Part Number *

Marking

Code

Part Number *

Marking

Code

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.

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

XXXXX

1AA
I/ML^^
820256

73871

7.1 Package Marking Information

MCP73871

3

e

3

e

© 2008 Microchip Technology Inc. DS22090A-page 25

MCP73871

/HDG3ODVWLF4XDG)ODW1R/HDG3DFNDJH0/±[[PP%RG\>4)1@

1RWHV

 3LQYLVXDOLQGH[IHDWXUHPD\YDU\EXWPXVWEHORFDWHGZLWKLQWKHKDWFKHGDUHD
 3DFNDJHLVVDZVLQJXODWHG
 'LPHQVLRQLQJDQGWROHUDQFLQJSHU$60(<0

%6& %DVLF'LPHQVLRQ7KHRUHWLFDOO\H[DFWYDOXHVKRZQZLWKRXWWROHUDQFHV
5() 5HIHUHQFH'LPHQVLRQXVXDOO\ZLWKRXWWROHUDQFHIRULQIRUPDWLRQSXUSRVHVRQO\

1RWH )RUWKHPRVWFXUUHQWSDFNDJHGUDZLQJVSOHDVHVHHWKH0LFURFKLS3DFNDJLQJ6SHFLILFDWLRQORFDWHGDW

KWWSZZZPLFURFKLSFRPSDFNDJLQJ

8QLWV 0,//,0(7(56

'LPHQVLRQ/LPLWV 0,1 120 0$;

1XPEHURI3LQV 1 

3LWFK H %6&

2YHUDOO+HLJKW $   

6WDQGRII $   

&RQWDFW7KLFNQHVV $ 5()

2YHUDOO:LGWK ( %6&

([SRVHG3DG:LGWK (   

2YHUDOO/HQJWK ' %6&

([SRVHG3DG/HQJWK '   

&RQWDFW:LGWK E   

&RQWDFW/HQJWK /   

&RQWDFWWR([SRVHG3DG .  ± ±

D

EXPOSED

PAD

E

E2

2

1

N

TOP VIEW

NOTE 1

N

L

K

b

e

D2

2

1

A

A1

A3

BOTTOM VIEW

0LFURFKLS 7HFKQRORJ\ 'UDZLQJ &%

DS22090A-page 26 © 2008 Microchip Technology Inc.

APPENDIX A: REVISION HISTORY

Revision A (July 2008)

• Original Release of this Document.

MCP73871

© 2008 Microchip Technology Inc. DS22090A-page 27

MCP73871

NOTES:

DS22090A-page 28 © 2008 Microchip Technology Inc.

PRODUCT IDENTIFICATION SYSTEM

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 = -40°C to +85°C

Package Type: ML = Plastic Quad Flat No Lead (QFN)

(4x4x0.9 mm Body), 20-lead

PART NO. XX

Output

Device

Options*

X/

Tem p.XXPackage

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

To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.

MCP73871

* Operational Output Options

Output

Options

1AA 4.10V Disable Disabled
1CA 4.10V 6 Disabled
1CC 4.10V 6 3.1
2AA 4.20V Disable Disabled
2CA 4.20V 6 Disabled
2CC 4.20V 6 3.1

* * Consult Factory for Alternative Device Options.

© 2008 Microchip Technology Inc. DS22090A-page 29

3CA 4.35V 6 Disabled
3CC 4.35V 6 3.1
4CA 4.40V 6 Disabled
4CC 4.40V 6 3.1

V

REG

Safety Timer

Duration (Hours)

LBO Voltage

Threshold (V)

MCP73871

NOTES:

DS22090A-page 30 © 2008 Microchip Technology Inc.

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.

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 BUT 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 otherwise, under any Microchip
intellectual property rights.

Trademarks

The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, K

EELOQ, KEELOQ logo, MPLAB, PIC, PICmicro,

PICSTAR T, rfPIC and SmartShunt are registered trademarks
of Microchip T echnology Incorporated in the U.S.A. and other
countries.

FilterLab, Linear Active Thermistor, MXDEV, MXLAB,
SEEVAL, SmartSensor and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A.

Analog-for-the-Digital Age, Application Maestro, CodeGuard,
dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
ECONOMONITOR, FanSense, In-Circuit Serial
Programming, ICSP, ICEPIC, Mindi, MiWi, MPASM, MPLAB
Certified logo, MPLIB, MPLINK, mTouch, PICkit, PICDEM,
PICDEM.net, PICtail, PIC

32

logo, PowerCal, PowerInfo,
PowerMate, PowerT ool, REAL ICE, rfLAB, Select Mode, Total
Endurance, UNI/O, WiperLock and ZENA 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.

All other trademarks mentioned herein are property of their
respective companies.

© 2008, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.

Printed on recycled paper.

Microchip received ISO/TS-16949:2002 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
T empe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the desig n
and manufacture of development systems is ISO 9001:2000 certified.

®

MCUs and dsPIC® DSCs, KEELOQ

®

code hopping

© 2008 Microchip Technology Inc. DS22090A-page 31

WORLDWIDE SALES AND SERVICE

AMERICAS

Corporate Office

2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: [phone]
Fax: [phone]
Technical Support:
http://support.microchip.com
Web Address:
www.microchip.com

Atlanta

Duluth, GA
Tel: [phone]
Fax: [phone]

Boston

Westborough, MA
Tel: [phone]
Fax: [phone]

Chicago

Itasca, IL
Tel: [phone]
Fax: [phone]

Dallas

Addison, TX
Tel: [phone]
Fax: [phone]

Detroit

Farmington Hills, MI
Tel: [phone]
Fax: [phone]

Kokomo

Kokomo, IN
Tel: [phone]
Fax: [phone]

Los Angeles

Mission Viejo, CA
Tel: [phone]
Fax: [phone]

Santa Clara

Santa Clara, CA
Tel: [phone]
Fax: [phone]

Toronto

Mississauga, Ontario,
Canada
Tel: [phone]
Fax: [phone]

ASIA/PACIFIC

Asia Pacific Office

Suites 3707-14, 37th Floor
Tower 6, The Gateway
Harbour City, Kowloon
Hong Kong
Tel: [phone]
Fax: [phone]

Australia - Sydney

Tel: [phone]
Fax: [phone]

China - Beijing

Tel: [phone]
Fax: [phone]

China - Chengdu

Tel: [phone]
Fax: [phone]

China - Hong Kong SAR

Tel: [phone]
Fax: [phone]

China - Nanjing

Tel: [phone]
Fax: [phone]

China - Qingdao

Tel: [phone]
Fax: [phone]

China - Shanghai

Tel: [phone]
Fax: [phone]

China - Shenyang

Tel: [phone]
Fax: [phone]

China - Shenzhen

Tel: [phone]
Fax: [phone]

China - Wuhan

Tel: [phone]
Fax: [phone]

China - Xiamen

Tel: [phone]
Fax: [phone]

China - Xian

Tel: [phone]
Fax: [phone]

China - Zhuhai

Tel: [phone]
Fax: [phone]

ASIA/PACIFIC

India - Bangalore

Tel: [phone]
Fax: [phone]

India - New Delhi

Tel: [phone]
Fax: [phone]

India - Pune

Tel: [phone]
Fax: [phone]

Japan - Yokohama

Tel: [phone]
Fax: [phone]

Korea - Daegu

Tel: [phone]
Fax: [phone]

Korea - Seoul

Tel: [phone]
Fax: [phone] or
82-2-558-5934

Malaysia - Kuala Lumpur

Tel: [phone]
Fax: [phone]

Malaysia - Penang

Tel: [phone]
Fax: [phone]

Philippines - Manila

Tel: [phone]
Fax: [phone]

Singapore

Tel: [phone]
Fax: [phone]

Taiwan - Hsin Chu

Tel: [phone]
Fax: [phone]

Taiwan - Kaohsiung

Tel: [phone]
Fax: [phone]

Taiwan - Taipei

Tel: [phone]
Fax: [phone]

Thailand - Bangkok

Tel: [phone]
Fax: [phone]

EUROPE

Austria - Wels

Tel: [phone]
Fax: [phone]

Denmark - Copenhagen

Tel: [phone]
Fax: [phone]

France - Paris

Tel: [phone]
Fax: [phone]

Germany - Munich

Tel: [phone]
Fax: [phone]

Italy - Milan

Tel: [phone]
Fax: [phone]

Netherlands - Drunen

Tel: [phone]
Fax: [phone]

Spain - Madrid

Tel: [phone]
Fax: [phone]

UK - Wokingham

Tel: [phone]
Fax: [phone]

01/02/08

DS22090A-page 32 © 2008 Microchip Technology Inc.