UCC28951QPWRQ1 - TEXAS INSTRUMENTS

 2007-2015 Microchip Technology Inc. DS20002071C-page 1

MCP73837/8

Features

• Highly Accurate Preset Voltage Regulation:

±0.5%

• Available Voltage Regulation Options:

- 4.20V, 4.35V, 4.4V or 4.5V

• Complete Linear Charge Management Controller:

- Autonomous Power Source Selection

- Integrated Pass Transistors

- Integrated Current Sense

- Integrated Reverse Discharge Protection

• Constant Current (CC)/Constant Voltage (CV)

Operation with Thermal Regulation

• Selectable USB Port Charge Current:

- Low: 1 Unit Load

- High: 5 Unit Loads

• Programmable AC Adapter Charge Current:

- 15 mA – 1000 mA

• Two-Charge Status Outputs

• Power-Good Monitor: MCP73837

• Timer Enable: MCP73838

• Automatic Recharge:

- Selectable Voltage Threshold

• Automatic End-of-Charge Control:

- Selectable Charge Termination Current Ratio

- Selectable Safety Timer Period

• Preconditioning of Deeply Depleted Cells – Can

Be Disabled

• Battery Cell Temperature Monitor

• UVLO (Undervoltage Lockout)

• Automatic Power-Down When Input Power Is

Removed

• Low-Dropout (LDO) Linear Regulator Mode

• Numerous Selectable Options Available for a

Variety of Applications:

- Refer to Section 1.0 “Electrical Characteris-

tics” for Selectable Options

- Refer to the “Product Identification System”

for Standard Options

• Temperature Range: -40°C to 85°C

• Packaging:

- 10-Lead 3 mm x 3 mm DFN

- 10-Lead MSOP*

* Consult the factory for MSOP availability.

Applications

• Smart Phones and Personal Data Assistants

(PDA)

• Portable Media Players (PMP)

• Ultra Mobile Devices (UMD)

• Digital Cameras

• MP3 Players

• Bluetooth Headsets

• Handheld Medical Devices

• AC/USB Dual Source Li-Ion Battery Chargers

Description

The MCP73837 and MCP73838 devices are fully

integrated linear Li-Ion/Li-Polymer battery chargers

with autonomous power source selection. Along with its

small physical size, the low number of external

components required makes the MCP73837/8 ideally

suitable for portable applications.

The MCP73837/8 automatically selects the USB port or

AC adapter as the power source for the system. For the

USB port powered systems, the MCP73837/8

specifically adheres to the current limits governed by

the USB specification. The host microcontroller can

select from two preset maximum charge current rates

of 100 mA (low-power USB port) or 500 mA

(high-power USB port). With an AC adapter providing

power to the system, an external resistor sets the mag-

nitude of the system or charge current up to a

maximum of 1A.

The MCP73837/8 employs a constant current/constant

voltage charge algorithm with selectable

preconditioning and charge termination. The constant

voltage regulation is fixed with four available options:

4.20V, 4.35V, 4.40V or 4.50V, to accommodate the new

emerging battery charging requirements. The

MCP73837/8 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 the reliability of the

device .

The MCP73837/8 are fully specified over the ambient

temperature range of -40°C to +85°C.

The MCP73837/8 devices are available in either a

3 mm x 3 mm 10-lead DFN package or a 10-lead

MSOP package.

Advanced Stand-Alone Li-Ion/Li-Polymer Battery Charge

Management Controller with Autonomous AC Adapter or

USB Port Source Selection

MCP73837/8

DS20002071C-page 2  2007-2015 Microchip Technology Inc.

Package Types

Typical Applications

PROG2

USB

STAT1 PG

(TE)

THERM

3x3 1

0-Lead DFN*

MCP73837/8

STAT2

110

BAT

PROG1 6

PROG2

VSS

VUSB

STAT1 PG (TE)

THERM

10-Lead MSOP

MCP73837/8

STAT2

10 VBAT

VAC

PROG1

*Includes Exposed Thermal Pad (EP); see Tab le 3 -1 .

STAT1

VAC

VSS

VBAT

Single

Li-Ion

Cell

MCP73837 Typical Application

4.7 µF

AC/DC Adapter

STAT2

THERMVUSB

PROG1

PROG2

USB Port

7Hi

Low

Thermistor

RPROG

1k

STAT1

VAC

VSS

VBAT

Cell

MCP73838 Typical Application

AC/DC Adapter

STAT2

THERMVUSB

PROG1

PROG2

USB Port

7Hi

Low

Thermistor

Low

1 K

K

4.7 µF

RPROG

 2007-2015 Microchip Technology Inc. DS20002071C-page 3

MCP73837/8

Functional Block Diagram (MCP73837/8)

Reference,

Bias, UVLO,

and SHDN

REF

(1.21V)

STAT1

PROG1

BAT

SENSEFET

G = 0.001

Vss

Direction

Control

175k

Precondition

TERM

111k

10k

157.3k

48k

470.6k

CHARGE

72.7k

310k

Current

Limit

LTVT

HTVT

470.6k

121k

THERM

ȝ$

Charge Control,

Timer,

and

Status Logic

STAT2

PG (TE)

LDO

175k

Direction

Control

ȝ$

10k 2k

100mA/500mA

SENSEFET

G = 0.001

SENSEFET

G = 0.001

SENSEFET

G = 0.001

REF

AC/USB

REG

UVLO

REG

PROG2

USB

MCP73837/8

DS20002071C-page 4  2007-2015 Microchip Technology Inc.

1.0 ELECTRICAL

CHARACTERISTICS

Absolute Maximum Ratings†

VDDN.................................................................................7.0V

All Inputs and Outputs w.r.t. VSS ............. -0.3 to (VDD +0.3)V

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) ...... ≥4kV

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 VDD= [VREG(typical) + 0.3V] to 6V, TA = -40°C to +85°C.

Typical values are at +25°C, VDD = [VREG (typical) + 1.0V].

Parameters Sym. Min. Typ. Max. Units Conditions

Supply Input

Supply Voltage VDD VREG(Typ)

+0.3V

—6V

(1)

Supply Current ISS — 1900 3000 µA Charging

— — 110 300 µA Charge Complete, No Battery

75 100 µA Standby (PROG Floating)

0.6 5 µA Shutdown (VDD ≤ VBAT – 100 mV

or VDD < VSTOP)

UVLO Start Threshold VSTART 3.35 3.45 3.55 V VDD = Low to High (USB Port)

UVLO Stop Threshold VSTOP 3.25 3.35 3.45 V VDD = High to Low (USB Port)

UVLO Hysteresis VHYS — 75 — mV (USB Port)

UVLO Start Threshold VSTART 4.1 4.15 4.3 V (AC Adapter)

UVLO Stop Threshold VSTOP 4.0 4.1 4.2 V (AC Adapter)

UVLO Hysteresis VHYS — 55 — mV (AC Adapter)

Voltage Regulation (Constant Voltage Mode)

Regulated Charge Voltage VREG 4.179 4.20 4.221 V VDD = [VREG(typical) + 1V]

— 4.328 4.35 4.372 V IOUT = 30 mA

4.378 4.40 4.422 V TA = -5°C to +55°C

4.477 4.50 4.523 V

Regulated Charge Voltage

Tolerance

VRTOL -0.5 — +0.5 % TA = -5°C to +55°C

Line Regulation VBAT/VBAT)

/VDD|

— 0.075 0.2 %/V VDD = [VREG(typical)+1V] to 6V

IOUT = 30 mA

Load Regulation VBAT/VBAT| — 0.150 0.3 % IOUT = 10 mA to 100 mA

VDD = [VREG(typical)+1V]

Supply Ripple Attenuation PSRR — 60 — dB IOUT = 10 mA, 10Hz to 1 kHz

——52—dBI

OUT = 10 mA, 10Hz to 10 kHz

—23—dBI

OUT = 10 mA, 10Hz to 1 MHz

Current Regulation (Fast Charge Constant-Current Mode)

AC Adapter Fast Charge Current IREG 95 105 115 mA PROG1 = 10 k

— 900 1000 1100 mA PROG1 = 1 k(2)

TA = -5°C to +55°C

Note 1: The supply voltage (VDD) = VAC when input power source is from AC adapter and the supply voltage (VDD) = VUSB

when input power source is from the USB port.

2: The value is guaranteed by design and not production tested.

3: The current is based on the ratio of selected current regulation (IREG).

The maximum charge impedance has to be less than shutdown impedance for normal operation.

 2007-2015 Microchip Technology Inc. DS20002071C-page 5

MCP73837/8

USB port Fast Charge Current IREG 80 90 100 mA PROG2 = Low

— 400 450 500 mA PROG2 = High

TA = -5°C to +55°C

Maximum Output Current Limit IMAX — 1200 — mA PROG1 < 833

Precondition Current Regulation (Trickle Charge Constant-Current Mode)

Precondition Current Ratio IPREG/IREG 7.5 10 12.5 % (3)

—152025%T

A = -5°C to +55°C

30 40 50 %

— 100 — %

Precondition Current Threshold

Ratio

VPTH/VREG 64 66.5 69 % VBAT Low to High

— 69 71.5 74 %

Precondition Hysteresis VPHYS — 120 — mV VBAT High to Low

Charge Termination

Charge Termination Current Ratio ITERM/IREG 3.75 5 6.25 % PROG1 = 1 kto 10 k

— 5.6 7.5 9.4 % TA = -5°C to +55°C

7.5 10 12.5 % (3)

15 20 25 %

Automatic Recharge

Recharge Voltage Threshold Ratio VRTH/VREG 92 94.0 96 % VBAT High to Low

—959799%T

A = -5°C to +55°C

Pass Transistor ON-Resistance

ON-Resistance RDSON — 350 — mVDD = 4.5V, TJ = +105°C

Battery Discharge Current

Output Reverse Leakage Current IDISCHARGE — 0.1 2 µA Standby (PROG1 or PROG2

Floating)

— — 0.55 2 µA Shutdown (VDD ≤ VBAT -100 mV

or VDD < VSTOP)

— -6 -15 µA Charge Complete

Status Indicators – STAT1, STAT2, PG (MCP73837)

Sink Current ISINK —1635mA

Low Output Voltage VOL —0.31VI

SINK = 4 mA

Input Leakage Current ILK — 0.03 1 µA High Impedance, VDD on pin

PROG1 Input (PROG1)

Charge Impedance Range RPROG 1——k(4)

Shutdown Impedance RPROG 70 — 200 kMinimum Impedance for

Shutdown

PROG2 Inputs (PROG2)

Input High Voltage Level VIH 0.8VDD ——%

Input Low Voltage Level VIL — — 0.2VDD %

Shutdown Voltage Level VSD 0.2VDD —0.8V

DD %

Input Leakage Current ILK —715µAV

PROG2 = VDD

DC CHARACTERISTICS (Continued)

Electrical Specifications: Unless otherwise indicated, all limits apply for VDD= [VREG(typical) + 0.3V] to 6V, TA = -40°C to +85°C.

Typical values are at +25°C, VDD = [VREG (typical) + 1.0V].

Parameters Sym. Min. Typ. Max. Units Conditions

Note 1: The supply voltage (VDD) = VAC when input power source is from AC adapter and the supply voltage (VDD) = VUSB

when input power source is from the USB port.

2: The value is guaranteed by design and not production tested.

3: The current is based on the ratio of selected current regulation (IREG).

The maximum charge impedance has to be less than shutdown impedance for normal operation.

MCP73837/8

DS20002071C-page 6  2007-2015 Microchip Technology Inc.

Timer Enable (TE)

Input High Voltage Level VIH 2——V

Input Low Voltage Level VIL ——0.8V

Input Leakage Current ILK —0.011µAV

TE = VDD

Thermistor Bias

Thermistor Current Source ITHERM 47 50 53 µA 2 k < RTHERM < 50 k

Thermistor Comparator

Upper Trip Threshold VT1 1.20 1.23 1.26 V VT1 Low to High

Upper Trip Point Hysteresis VT1HYS —-40—mV

Lower Trip Threshold VT2 0.235 0.250 0.265 V VT2 High to Low

Lower Trip Point Hysteresis VT2HYS —40—mV

System Test (LDO) Mode

Input High Voltage Level VIH ——V

DD – 0.1 V

THERM Input Sink Current ISINK 3 5.5 20 µA Stand-by or System Test Mode

Bypass Capacitance CBAT 1

4.7

——µF

µF

IOUT < 250 mA

IOUT > 250 mA

Automatic Power Down (SLEEP Comparator, Direction Control)

Automatic Power Down Entry

Threshold

VPD VBAT +

10 mV

VBAT +

100 mV

—V2.3V ≤ VBAT ≤ VREG

VDD Falling

Automatic Power Down Exit

Threshold

VPDEXIT —V

BAT +

150 mV

VBAT +

250 mV

V2.3V ≤ VBAT ≤ VREG

VDD Rising

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 VDD= [VREG(typical) + 0.3V] to 6V, TA = -40°C to +85°C.

Typical values are at +25°C, VDD = [VREG (typical) + 1.0V].

Parameters Sym. Min. Typ. Max. Units Conditions

Note 1: The supply voltage (VDD) = VAC when input power source is from AC adapter and the supply voltage (VDD) = VUSB

when input power source is from the USB port.

2: The value is guaranteed by design and not production tested.

3: The current is based on the ratio of selected current regulation (IREG).

The maximum charge impedance has to be less than shutdown impedance for normal operation.

 2007-2015 Microchip Technology Inc. DS20002071C-page 7

MCP73837/8

AC CHARACTERISTICS

TEMPERATURE SPECIFICATIONS

Electrical Specifications: Unless otherwise indicated, all limits apply for VDD = [VREG (typical) + 0.3V] 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 msV

BAT < VPTH to VBAT > VPTH

Current Rise Time Out of Precondition tRISE ——10 msI

OUT 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 0 0 Hours Timer Disabled

— 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 µs ISINK = 1mA to 0mA

Status Output Turn-on tON — — 500 µs ISINK = 0mA to 1mA

Electrical Specifications: Unless otherwise indicated, all limits apply for VDD = [VREG (typ.) + 0.3V] to 6V.

Typical values are at +25°C, VDD = [VREG (typ.) + 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, 10-Lead MSOP JA — 113 — °C/W 4-Layer JC51-7 Standard Board,

Natural Convection(1)

Thermal Resistance, 10-Lead 3 x 3 DFN JA — 41 — °C/W 4-Layer JC51-7 Standard Board,

Natural Convection

Note 1: This represents the minimum copper condition on the Printed Circuit Board (PCB).

MCP73837/8

DS20002071C-page 8  2007-2015 Microchip Technology Inc.

2.0 TYPICAL PERFORMANCE CURVES

Note: Unless otherwise indicated, VDD = [VREG(typical) + 1V], IOUT = 30 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: Output Leakage Current

(IDISCHARGE) vs. Battery Regulation Voltage

(VBAT).

FIGURE 2-4: Output Leakage Current

(IDISCHARGE) vs. Ambient Temperature (TA).

FIGURE 2-5: Output Leakage Current

(IDISCHARGE) vs. Battery Voltage (VBAT).

FIGURE 2-6: Charge Current (IOUT) vs.

Programming Resistor (RPROG).

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.

4.160

4.165

4.170

4.175

4.180

4.185

4.190

4.195

4.200

4.205

4.210

4.5 4.8 5.0 5.3 5.5 5.8 6.0

Supply Voltage (V)

Battery Regulation Voltage (V)

TEMP = 25°C

IOUT = 10 mA

IOUT = 100 mA

OUT

= 500 mA

IOUT = 1000 mA

IOUT = 50 mA

4.170

4.175

4.180

4.185

4.190

4.195

4.200

4.205

4.210

-40-30-20-100 1020304050607080

Ambient Temperature (°C)

Battery Regulation Voltage (V)

IOUT = 10 mA VDD

= 5.2V

IOUT = 1000 mA

IOUT = 500 mA

IOUT = 100 mA

IOUT = 50 mA

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2

Battery Voltage (V)

Output Leakage Current (µA)

VDD = VBAT

TEMP = 25 °C

0.0

0.4

0.8

1.2

1.6

2.0

-40-30-20-10 0 1020304050607080

Temperature (°C)

Output Leakage Current (µA)

VDD = Floating

VBAT = 4.2V

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2

Battery Voltage (V)

Output Leakage Current (µA)

VDD = Floating

TEMP = +25°C

100

200

300

400

500

600

700

800

900

1000

1 6 11 16 21 26 31 36 41 46 51 56 61

RPROG (kΩ)

IREG (mA)

VDD = 5.2V

Temp = 25°C

 2007-2015 Microchip Technology Inc. DS20002071C-page 9

MCP73837/8

Note: Unless otherwise indicated, VDD = [VREG(typical) + 1V], IOUT = 30 mA and TA= +25°C, Constant-voltage mode.

FIGURE 2-7: Charge Current (IOUT) vs.

Supply Voltage (VDD).

FIGURE 2-8: Charge Current (IOUT) vs.

Supply Voltage (VDD).

FIGURE 2-9: Charge Current (IOUT) vs.

Ambient Temperature (TA).

FIGURE 2-10: Charge Current (IOUT) vs.

Ambient Temp eratu re (TA).

FIGURE 2-11: Charge Current (IOUT) vs.

Ambient Temp eratu re (TA).

FIGURE 2-12: Charge Current (IOUT) vs.

Junction Temperature (TJ).

700

750

800

850

900

950

1000

1050

1100

1150

1200

4.5 4.8 5.0 5.3 5.5 5.8 6.0

Supply Voltage (V)

Charge Current (mA)

RPROG = 1 kΩ

Temp = +25°C

100

102

104

4.5 4.8 5.0 5.3 5.5 5.8 6.0

Supply Voltage (V)

Charge Current (mA)

RPROG = 10 kΩ

Temp = +25°C

700

750

800

850

900

950

1000

1050

1100

-40-30-20-100 1020304050607080

Ambient Temperature (°C)

Charge Current (mA)

RPROG = 1 kΩ

VDD = 5.2V

100

102

104

106

108

110

-40-30-20-10 0 1020304050607080

Ambient Temperature (°C)

Charge Current (mA)

RPROG = 10 kΩ

VDD = 5.2V

-40-30-20-100 1020304050607080

Ambient Temperature (°C)

Charge Current (mA)

RPROG = 20 kΩ

VDD = 5.2V

100

200

300

400

500

600

700

800

900

1000

1100

1200

105

115

125

135

145

155

Junction Temperature (°C)

Charge Current (mA)

RPROG = 1 kΩ

MCP73837/8

DS20002071C-page 10  2007-2015 Microchip Technology Inc.

Note: Unless otherwise indicated, VDD = [VREG(typical) + 1V], IOUT = 30 mA and TA= +25°C, Constant-voltage mode.

FIGURE 2-13: Charge Current (IOUT) vs.

Junction Temperature (TJ).

FIGURE 2-14: Charge Current (IOUT) vs.

Junction Temperature (TJ).

FIGURE 2-15: Thermistor Current (ITHERM)

vs. Supply Voltage (VDD).

FIGURE 2-16: Thermistor Current (ITHERM)

vs. Ambient Temperature (TA).

FIGURE 2-17: Power Supply Ripple

Rejection (PSRR).

FIGURE 2-18: Power Supply Ripple

Rejection (PSRR).

100

150

200

250

300

350

400

450

500

550

600

105

115

125

135

145

155

Junction Temperature (°C)

Charge Current (mA)

RPROG = 2 kΩ

100

110

120

105

115

125

135

145

155

Junction Temperature (°C)

Charge Current (mA)

RPROG = 10 kΩ

47.0

47.5

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

4.5 4.8 5.0 5.3 5.5 5.8 6.0

Supply Voltage (V)

Thermistor Current (mA)

Temp = +25°C

47.0

47.5

48.0

48.5

49.0

49.5

50.0

50.5

51.0

51.5

52.0

-40

-30

-20

-10

Ambient Temperature (°C)

Thermistor Current (mA)

VDD = 5.2V

-70

-60

-50

-40

-30

-20

-10

0.01 0.1 1 10 100 1000

Frequency (kHz)

Attenuation (dB)

IOUT = 10 mA

COUT = 4.7 µF

-70

-60

-50

-40

-30

-20

-10

0.01 0.1 1 10 100 1000

Frequency (kHz)

Attenuation (dB)

IOUT = 100 mA

COUT = 4.7 µF

 2007-2015 Microchip Technology Inc. DS20002071C-page 11

MCP73837/8

Note: Unless otherwise indicated, VDD = [VREG(typical) + 1V], IOUT = 30 mA and TA= +25°C, Constant-voltage mode.

FIGURE 2-19: Line Transient Response.

FIGURE 2-20: Line Transient Response.

FIGURE 2-21: Load Transient Response.

FIGURE 2-22: Load Transient Response.

FIGURE 2-23: VAC Start Delay

(IOUT = 1A).

FIGURE 2-24: VUSB Star t Del ay

(USB = Low).

-200

-100

100

200

300

400

500

600

700

Time (µs)

Input Source (V)

-0.5

-0.4

-0.3

-0.2

-0.1

0.1

Output Ripple (V)

IOUT = 100 mA

VOUT

VIN

-200

-100

100

200

300

400

500

600

700

800

Time (µs)

Input Source (V)

-0.5

-0.4

-0.3

-0.2

-0.1

0.1

Output Ripple (V)

IOUT = 10 mA

VOUT

VIN

-0.05

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-4.0E-04

-2.0E-04

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

1.6E-03

Time (Minutes)

Output Current (A)

-0.12

-0.1

-0.08

-0.06

-0.04

-0.02

0.02

0.04

Output Ripple (V)

IOUT = 10 mA

IOUT

VOUT(AC)

-0.1

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-4.0E-04

-2.0E-04

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

1.6E-03

Time (Minutes)

Output Current (A)

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0.05

0.1

Output Ripple (V)

IOUT = 100 mA

IOUT

VOUT

VIN

VOUT

VIN

VOUT

MCP73837/8

DS20002071C-page 12  2007-2015 Microchip Technology Inc.

Note: Unless otherwise indicated, VDD = [VREG(typical) + 1V], IOUT = 30 mA and TA= +25°C, Constant-voltage mode.

UVLOVAC

FIGURE 2-25: VUSB Start Delay

(USB = High)

FIGURE 2-26: Complete Charge Cycle

(1200 mAh Li-Ion Battery).

FIGURE 2-27: Typical Charge Profile in

Thermal Regulation (1200 mAh Li-Ion Battery).

FIGURE 2-28: Complete Charge Cycle

(180 mAh Li-Ion Battery).

FIGURE 2-29: Typical Charge Profile in

Preconditioning and CC-CV (180 mAh Li-Ion

Battery).

VIN

VOUT

0.0

1.0

2.0

3.0

4.0

5.0

100

110

120

130

140

150

Time (Minutes)

Battery Voltage (V)

0.2

0.4

0.6

0.8

1.2

Charge Current (A)

VDD = 5.2V

RPROG = 1 kΩ

1200 mAh Li-Ion Battery

VOUT

IOUT

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

012345678910

Time (Minutes)

Battery Voltage (V)

0.3

0.6

0.9

1.2

Charge Current (A)

VDD = 5.2V

RPROG = 1 kΩ

1200 mAh Li-Ion Battery

VOUT

IOUT

0.0

1.0

2.0

3.0

4.0

5.0

0 20 40 60 80 100 120 140 160 180

Time (Minutes)

Battery Voltage (V)

0.02

0.04

0.06

0.08

0.1

0.12

Charge Current (A)

VDD = 5.2V

RPROG = USB_Low

180 mAh Li-Ion Battery

VOUT

IOUT

0.0

1.0

2.0

3.0

4.0

5.0

012345678910

Time (Minutes)

Battery Voltage (V)

0.02

0.04

0.06

0.08

0.1

0.12

Charge Current (A)

VDD = 5.2V

RPROG = USB_Low

180 mAh Li-Ion Battery

C.C. Begins

Preconditioning

C.V. Begins

VOUT

IOUT

 2007-2015 Microchip Technology Inc. DS20002071C-page 13

MCP73837/8

3.0 PIN DESCRIPTION

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

TABLE 3-1: PIN FUNCTION TABLE

3.1 AC Adapter Supply Input (VAC)

A supply voltage of VREG + 0.3V to 6V from the AC/DC

wall-adapter is recommended. When both the AC

adapter and the USB port supply voltages are present

at the same time, the AC adapter dominates the regu-

lated charge current with the maximum value of 1A.

Bypass to VSS, with a minimum of 4.7 µF, is

recommended.

3.2 USB Port Supply Input (VUSB)

A supply voltage of VREG + 0.3V to 6V from the USB

port is recommended. When no supply voltage from

VAC pin is available, the Li-Ion battery is charged

directly from USB port. Bypass to VSS, with a minimum

of 1 µF, is recommended.

3.3 Charge Status Output 1 (STAT1)

STAT1 is an open-drain logic output for connection to a

LED for charge status indication. Alternatively, a pull-up

resistor can be applied for interfacing to a host

microcontroller.

3.4 Charge Status Output 2 (STAT2)

STAT2 is an open-drain logic output for connection to a

LED for charge status indication. Alternatively, a pull-up

resistor can be applied for interfacing to a host

microcontroller.

3.5 Battery Management 0V Reference

(VSS)

Connect to the negative terminal of the battery and

input supply.

3.6 AC Adapter Current Regulation

Set (PROG1)

The AC adapter constant charge current is set by

placing a resistor from PROG1 to VSS. PROG1 is the

set point of precondition and termination when the AC

adapter is present.

PROG1 also functions as device charge control

enable. The MCP73837/8 is shut down when an

impedance value greater than 70 k is applied to

PROG1. When PROG1 is floating, the MCP73837/8

enters into Stand-By mode.

Pin Number

Symbol I/O Function

DFN-10 MSOP-10

11V

AC I AC Adapter Supply Input

22V

USB I USB port Supply Input

3 3 STAT1 O Charge Status Output 1 (Open-Drain)

4 4 STAT2 O Charge Status Output 2 (Open-Drain)

55V

SS — Battery Management 0V Reference

6 6 PROG1 I/O Current Regulation Setting With AC Adapter; Device Charge Control Enable;

Precondition Set Point for AC control

7 7 PROG2 I Current Regulation Setting With USB Port; Precondition Set Point for USB

control.

PG O Available on MCP73837: Power-Good Status Output (Open-Drain)

TE I Available on MCP73838: Timer Enable; Enables Safety Timer (Active Low)

9 9 THERM I/O Thermistor Monitoring Input and Bias current; System Test (LDO) Mode Input

10 10 VBAT I/O Battery Positive Input and Output Connection

11 — EP — 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 PCB.

MCP73837/8

DS20002071C-page 14  2007-2015 Microchip Technology Inc.

3.7 USB Port Current Regulation Set

(PROG2)

The MCP73837/8 USB port current regulation set input

(PROG2) is a digital input selection. A logic Low selects

a 1 unit load charge current; a logic High selects a 5

unit loads charge current. The precondition and termi-

nation current is internally set to the percentage levels

selected by the device part number. The current is

based on the selected unit load charge current, based

on the level of PROG2.

PROG2 also functions as the set point of termination

when the USB port is present. When PROG2 is float-

ing, the MCP73837/8 enters into Stand-By mode.

3.8 Power Good (PG)

Power Good (PG) is available only on MCP73837. PG

is an open-drain logic output for connection to an LED

for input power supply indication. Alternatively, a

pull-up resistor can be applied for interfacing to a host

microcontroller.

3.9 Timer Enable (TE)

Timer Enable (TE) is available only on MCP73838. TE

enables the built-in safety timer when it is pulled Low,

and disables the built-in safety timer when it is pulled

High.

3.10 Battery Temperature Monitor

(THERM)

MCP73837/8 continuously monitors the 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 the most

common 10 k negative-temperature coefficient

thermistors (NTC).

3.11 Battery Charge Control Output

(VBAT)

Connect to the positive terminal of Li-Ion/Li-Polymer

batteries. Bypass to VSS, with a minimum of 1 µF, to

ensure loop stability when the battery is disconnected.

3.12 Exposed Thermal Pad (EP)

The 10-lead 3 x 3 mm DFN package has an exposed

metal pad on the bottom of the package. It gives the

device better thermal characteristics by providing a

good thermal path to a PCB ground plane.There is an

internal electrical connection between the EP and the

VSS pin; they must be connected to the same potential

on the PCB.

Note: The built-in safety timer is available for

both MCP73837 and MCP73838 in the

following options: Disable, 4 HR, 6 HR,

and 8 HR.

 2007-2015 Microchip Technology Inc. DS20002071C-page 15

MCP73837/8

4.0 DEVICE OVERVIEW

The MCP73837/8 devices are simple, yet fully integrated, linear charge management controllers. Figure 4-1 depicts

the operational flow algorithm.

FIGURE 4-1: Operational Algorithm.

VBAT > VPTH

SHUTDOWN MODE*

VDD



VBAT

100 mV

VDD < VSTOP

STAT2 = High Z

PG = High Z

PRECONDITIONING MODE

Charge Current = IPREG

STAT1 = LOW

STAT2 = High Z

PG = LOW

Timer Reset

FAST CHARGE MODE

Charge Current = IREG

STAT1 = LOW

STAT2 = High Z

PG = LOW

Timer Enabled

CONSTANT VOLTAGE MODE

Charge Voltage = VREG

STAT1 = LOW

STAT2 = High Z

PG = LOW

CHARGE COMPLETE MODE

No Charge Current

STAT1 = High Z

STAT2 = LOW

PG = LOW

Timer Expired

STANDBY MODE *

VDD > (VREG + 100 mV)

PROG > 200 k



STAT1 = High Z

STAT2 = High Z

PG = LOW

Continuously Monitored

TEMPERATURE FAULT

No Charge Current

STAT1 = High Z

STAT2 = High Z

PG = LOW

Timer Suspended

SYSTEM TEST (LDO) MODE

VTHERM > (VDD -100 mV)

STAT1 = LOW

STAT2 = LOW

PG = LOW

Timer Suspended

TIMER FAULT

No Charge Current

STAT1 = High Z

STAT2 = High Z

PG = LOW

Timer Suspended

Timer Expired

STAT1 = High Z

VBAT < VPTH

VBAT > VPTH

VBAT = VREG

VBAT < VRTH

IBAT < ITERM

MCP73837/8

DS20002071C-page 16  2007-2015 Microchip Technology Inc.

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. The UVLO circuitry has a built-in

hysteresis of 75 mV for the USB port and 55 mV for the

AC adapter.

In the event a battery is present when the input power

is applied, the input supply must rise 100 mV above the

battery voltage before MCP73837/8 becomes

operational.

The UVLO circuit places the device in shutdown mode

if the input supply falls to within +100 mV of the battery

voltage.

The UVLO circuit is always active. If, at any time, the

input supply is below the UVLO threshold or within

+100 mV of the voltage at the VBAT pin, the

MCP73837/8 is placed in a Shutdown mode.

During any UVLO condition, the battery reverse

discharge current is less than 2 µA.

4.2 Autonomous Power Source

Selection

The MCP73837/8 devices are designed to select the

USB port or AC adapter as the power source

automatically. If the AC adapter input is not present, the

USB port is selected. If both inputs are available, the

AC adapter has first priority.

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 con-

nected from PROG1 to VSS. If the PROG1 or PROG2

pin are open or floating, the MCP73837/8 is disabled

and the battery reverse discharge current is less than

2 µA. In this manner, the PROG1 pin acts as a charge

enable and can be used as a manual shutdown.

4.4 Preconditioning

If the voltage at the VBAT pin is less than the

preconditioning threshold, the MCP73837/8 enters a

preconditioning mode. The preconditioning threshold is

factory set.

Refer to Section 1.0 “Electrical Characteristics” for pre-

conditioning threshold options.

In this mode, the MCP73837/8 supplies a percentage

of the charge current (established with the value of the

resistor connected to the PROG1 pin for AC mode,

established by PROG2 level for USB mode) to the bat-

tery. The percentage or ratio of the current is factory

set. Refer to Section 1.0 “Electrical Characteristics” for

preconditioning current options.

When the voltage at the VBAT pin rises above the

preconditioning threshold, the MCP73837/8 enters the

Constant Current or Fast Charge mode.

4.5 Constant Current Mode – Fast

Charge

During Constant Current mode, the programmed (AC

adapter) or selected (USB port) charge current is sup-

plied to the battery or load.

For AC adapter, the charge current is established

using a single resistor from PROG1 to VSS. The

program resistor and the charge current are calculated

using the Equation 4-1.

EQUATION 4-1:

When charging from a USB port, the host

microcontroller has the option of selecting either a

one-unit-load or a five-unit-loads charge rate based on

the PROG2 input. A logic Low selects a one-unit-load

charge rate, a High selects a five-unit-loads charge

rate, and high impedance input suspends or disables

charging.

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.

Note: If the input power is switched during a

charge cycle, the power path switch-over

will be a break-before-make connection.

As a result, the charge current can

momentarily go to zero. The charge cycle

timer will remain continuous.

Note: USB Specification Rev. 2.0 defines the

maximum absolute current for one unit

load is 100 mA. This value is not an

average over time and cannot be

exceeded.

IREG 1000V

RPROG

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

Where:

RPROG = kilohm (k

IREG = milliampere (mA)

 2007-2015 Microchip Technology Inc. DS20002071C-page 17

MCP73837/8

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 MCP73837/8 remains in

this condition until the battery is removed, the input

battery is removed or the PROG1/2 pin is opened. If the

battery is removed or the PROG1/2 pin is opened, the

MCP73837/8 enters the Stand-by mode where it

remains until a battery is reinserted or the PROG1/2 pin

is reconnected. If the input power is removed, the

MCP73837/8 is in Shutdown. When the input power is

reapplied, a normal start-up sequence begins.

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 4.20V,

4.35V, 4.40V, or 4.5V, with a tolerance of ± 0.5%.

4.7 Charge Termination

The charge cycle is terminated when, during constant

voltage mode, the average charge current diminishes

below a percentage of the programmed charge current,

or the internal timer has expired. A 1 ms filter time on

the termination comparator ensures that transient load

conditions do not result in premature charge cycle ter-

mination. The percentage or ratio of the current is fac-

tory set. The timer period is factory set and can be

disabled. Refer to Section 1.0 “Electrical Characteris-

tics” for charge termination current ratio and timer

period options.

The charge current is latched off and the MCP73837/8

enters a charge complete mode.

4.8 Automatic Recharge

The MCP73837/8 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 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.

4.9 Thermal Regulation

The MCP73837/8 limits the charge current based on

the die temperature. The thermal regulation optimizes

the charge cycle time while maintaining device

reliability. Figure 4-2 depicts the thermal regulation for

the MCP73837/8. Refer to Section 1.0 “Electrical

Characteristics” for thermal package resistances and

Section 6.1.1.3 “Thermal Considerations” for

calculating power dissipation.

FIGURE 4-2: Thermal Regulation.

4.10 Thermal Shutdown

The MCP73837/8 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.

Note: Charge termination and automatic

recharge features avoid constantly

charging a Li-Ion battery in order to pro-

long its life, while keeping its capacity at a

healthy level.

100

200

300

400

500

600

700

800

900

1000

1100

1200

25 35 45 55 65 75 85 95 105 115 125 135 145 155

Junction Temperature (°C)

Charge Current (mA)

RPROG = 1 kΩ

MCP73837/8

DS20002071C-page 18  2007-2015 Microchip Technology Inc.

5.0 DETAILED DESCRIPTION

•Analog Circuitry

•Digital Circuitry

5.1 Analog Circuitry

5.1.1 BATTERY MANAGEMENT INPUT

SUPPLY (VDD)

The VDD input is the input supply to the MCP73837/8.

The MCP73837/8 can be supplied by either AC adapter

(VAC) or USB port (VUSB) with autonomous source

selection. The MCP73837/8 automatically enters a

Power-Down mode if the voltage on the VDD input falls

to within +100 mV of the battery voltage or below the

UVLO voltage (VSTOP). This feature prevents draining

the battery pack when both the VAC and VUSB supplies

are not present.

5.1.2 AC ADAPTER CURRENT

REGULATION SET (PROG1)

For the MCP73837/8, the charge current regulation

can be scaled by placing a programming resistor

(RPROG) from the PROG1 input to VSS. The program

resistor and the charge current are calculated using

the following equation:

EQUATION 5-1:

The preconditioning current and the charge

termination current are ratiometric to the fast charge

current based on the selected device options.

5.1.3 BATTERY CHARGE CONTROL

OUTPUT (VBAT)

The battery charge control output is the drain terminal

of an internal P-channel MOSFET. The MCP73837/8

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 MCP73837/8 continuously monitors battery

temperature during a charge cycle by measuring the

voltage between the THERM and the VSS pins. An

internal 50 µA current source provides the bias for the

most common 10 k negative-temperature coefficient

(NTC) or positive-temperature coefficient (PTC)

thermistors. The current source is controlled, avoiding

measurement sensitivity to fluctuations in the supply

voltage (VDD). The MCP73837/8 compares the voltage

at the THERM pin to factory set thresholds of 1.20V

and 0.25V, typically. If a voltage that is outside the

thresholds is detected during a charge cycle, the

MCP73837/8 immediately suspends the charge cycle.

The MCP73837/8 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.

5.1.5 SYSTEM TEST (LDO) MODE

The MCP73837/8 can be placed in a System Test

mode. In this mode, the MCP73837/8 operates as a

low dropout (LDO) linear regulator. The output voltage

is regulated to the factory set voltage regulation option.

The available output current is limited to the pro-

grammed fast charge current. For stability, the VBAT

output must be bypassed to VSS with a minimum

capacitance of 1 µF for output currents up to 250 mA.

A minimum capacitance of 4.7 µF is required for output

currents above 250 mA.

The system test mode is entered by driving the THERM

input greater than (VDD – 100 mV) with no battery

connected to the output. In this mode, the MCP73837/8

can be used to power the system without a battery

being present.

IREG 1000V

RPROG

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

Where:

RPROG = kilohm (k

IREG = milliampere (mA

Note 1: ITHERM is disabled during shutdown,

stand-by, and system test modes.

2: A pull-down current source on the

THERM input is active only in Stand-By

and System Test modes.

3: During System Test mode, the PROG

input sets the available output current

limit.

4: System Test mode shall be exited by

releasing the THERM input or cycling

input power.

 2007-2015 Microchip Technology Inc. DS20002071C-page 19

MCP73837/8

5.2 Digital Circuitry

5.2.1 STATUS INDICATORS AND POWER

GOOD (PG) OPTION

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.

5.2.2 USB PORT CURRENT

REGULATION SELECT (PROG2)

For the MCP73837/8, driving the PROG2 input to a

logic Low selects the low charge current setting

(maximum 100 mA). Driving the PROG2 input to a logic

High selects the high charge current setting (maximum

500 mA).

The Precondition current and Termination current are

percentages of the charge current selected by the

PROG2 level. The percentage is based on the selected

part number of the device.

5.2.3 POWER GOOD (PG) OPTION

The power good (PG) option is a pseudo open-drain

output. It is only available on the MCP73837. The PG

output can sink current, but not source current. How-

ever, there is a diode path back to the input, and as

such, the output should be pulled up only to the input.

The PG output is low whenever the input to the

MCP73837 is above the UVLO threshold and greater

than the battery voltage. If the supply voltage is above

the UVLO, but below VREG(typical)+0.3V, the

MCP73837 will pulse the PG output as the device

determines if a battery is present.

5.2.4 TIMER ENABLE (TE) OPTION

The timer enable (TE) input option is used to enable or

disable the internal timer. It is only available on the

MCP73838. A low signal on this pin enables the inter-

nal 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.

5.2.5 DEVICE DISABLE (PROG1/2)

The current regulation set input pin (PROG1/2) can be

used to terminate a charge at any time during the

charge cycle, as well as to initiate a charge cycle or to

initiate a recharge cycle.

Placing a programming resistor from the PROG1/2

input to VSS enables the device. Allowing the PROG1/2

input to float or applying a logic-high input signal to

PROG1 disables the device and terminates a charge

cycle. When disabled, the device’s supply current is

reduced to 75 µA, typically.

TABLE 5-1: STATUS OUTPUTS

Charge Cycle State STAT1 STAT2 PG

Shutdown High Z High Z High-Z

Standby High-Z High Z L

Preconditioning L High Z L

Constant Current L High Z L

Constant Voltage L High Z L

Charge Complete – Standby High Z L L

Temperature Fault High Z High Z L

Timer Fault High Z High Z L

System Test Mode L L L

MCP73837/8

DS20002071C-page 20  2007-2015 Microchip Technology Inc.

6.0 APPLICATIONS

The MCP73837/8 devices are designed to operate in

conjunction with a host microcontroller or in

stand-alone applications. The MCP73837/8 devices

provide the preferred charge algorithm for Lithium-Ion

and Lithium-Polymer cells, Constant-Current followed

by Constant-Voltage. Figure 6-1 depicts a typical

stand-alone MCP73837 application circuit, while

Figure 6-2 and Figure 6-3 depict the accompanying

charge profile.

FIGURE 6-1: MCP73837 Typical Stand-Alone Application Circuit.

FIGURE 6-2: Typica l Charge Prof il e

(1200 mAh Li-Ion Battery). FIGURE 6-3: Typical Charge Profile in

Thermal Regulation (1200 mAh Li-Ion Battery).

STAT1

VAC

/PG

VBAT

Single

Li-Ion

Cell

MCP73837

STAT2

THERMVUSB

PROG1

PROG2

USB Port

7Hi

Low

Thermistor

RPROG



REGULATED

WALL CUBE

CIN1

CIN2

COUT

0.0

1.0

2.0

3.0

4.0

5.0

100

110

120

130

140

150

Time (Minutes)

Battery Voltage (V)

0.2

0.4

0.6

0.8

1.2

Charge Current (A)

VDD = 5.2V

RPROG = 1 kΩ

1200 mAh Li-Ion Battery

IOUT

VOUT

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

012345678910

Time (Minutes)

Battery Voltage (V)

0.3

0.6

0.9

1.2

Charge Current (A)

VDD = 5.2V

RPROG = 1 kΩ

1200 mAh Li-Ion Battery

VOUT

IOUT

 2007-2015 Microchip Technology Inc. DS20002071C-page 21

MCP73837/8

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 transi-

tioned 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 guidance from

battery manufacturers. For example, programming

700 mA fast charge current for a 1000 mAh Li-Ion

battery pack if its preferred fast charge rate is 0.7C.

This will result in the shortest charge cycle time without

degradation of a battery's life and performance.

6.1.1.2 Input Over-Voltage Protection

Input over-voltage protection must be used when the

input power source is hot-pluggable. This includes USB

cables and wall-type power supplies. The cabling of

these supplies acts as an inductor. When the supplies

are connected/ disconnected from the system, large

voltage transients are created which may damage the

system circuitry. These transients should be snubbed

out. A TransZorb® diode (unidirectional or bidirec-

tional), connected from the VAC and VUSB inputs to 0V

ground reference, will snub the transients. An example

of this can be shown in Figure 6-4.

FIGURE 6-4: Input Over-Voltage Protection Example.

STAT1

VAC

VSS

/PG

VBAT

Single

Li-Ion

Cell

MCP73837

STAT2

THERMVUSB

PROG1

PROG2

USB Port

7Hi

Low

Thermistor

RPROG

1 kΩ

kΩ

REGULATED

5V WALL CUBE

IN1

CIN2

COUT

SMAJ5.0A/AC

MCP73837/8

DS20002071C-page 22  2007-2015 Microchip Technology Inc.

6.1.1.3 Thermal Considerations

The worst-case power dissipation in the battery char-

ger 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 a 500 mA, ±10% fast charge

current is calculated in the following example:

EXAMPLE 6-1:

This power dissipation with the battery charger in the

MSOP-10 package will cause thermal regulation to be

entered as depicted in Figure 6-3. Alternatively, the

3 mm x 3 mm DFN package could be utilized to reduce

the charge cycle times.

6.1.1.4 External Capacitors

The MCP73837/8 is stable with or without a battery

load. In order to maintain good AC stability in the Con-

stant Voltage mode, a minimum capacitance of 1 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 interconnec-

tions appear inductive at high frequencies. These ele-

ments 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, independent of the capacitor’s minimum Effec-

tive Series Resistance (ESR) value. The actual value of

the capacitor (and its associated ESR) depends on the

output load current. A 1 µF ceramic, tantalum, or alumi-

num electrolytic capacitor at the output is usually suffi-

cient to ensure stability for output currents up to

500 mA.

6.1.1.5 Reverse-Blocking Protection

The MCP73837/8 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.

6.1.1.6 Charge Inhibit

The current regulation set input pin (PROG1/2) can be

used to terminate a charge at any time during the

charge cycle, as well as to initiate a charge cycle or a

recharge cycle.

Placing a programming resistor from the PROG1 input

to VSS or driving PROG2 to logic High or Low enables

the device. Allowing either the PROG1/2 input to float

disables the device and terminates a charge cycle.

When disabled, the device’s supply current is reduced

to 75 µA, typically.

6.1.1.7 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 in order to set the

temperature window of interest.

For NTC thermistors, see Equation 6-2.

EQUATION 6-2:

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°C – +50°C

by placing a 1.54 k resistor in series (RT1), and a

69.8 k resistor in parallel (RT2) with the thermistor.

6.1.1.8 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 or Figure 4-1 for information on the state of

the status output during a charge cycle.

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–550mA



1.54W==

24k



RT1 RT2 RCOLD



RT2 R+ COLD

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



RT1 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

 2007-2015 Microchip Technology Inc. DS20002071C-page 23

MCP73837/8

6.2 PCB Layout Issues

For optimum voltage regulation, place the battery pack

as close as possible to the device’s VBAT and VSS pins.

This is recommended to minimize voltage drops along

the high-current-carrying PCB traces.

If the PCB layout is used as a heat sink, adding many

vias in the heatsink pad can help conduct more heat to

the backplane of the PCB, thus reducing the maximum

junction temperature.

MCP73837/8

DS20002071C-page 24  2007-2015 Microchip Technology Inc.

7.0 PACKAGING INFORMATION

7.1 Package Marking Information

10-Lead DFN

10-Lead MSOP Example:

Example:

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.

Part Number(1)Marking

Code Part Number(1)Marking

Code

MCP73837-FCI/MF BABA MCP73837T-FCI/MF BABA

MCP73837-FJI/MF BABB MCP73837T-FJI/MF BABB

MCP73837-NVI/MF BABC MCP73837T-NVI/MF BABC

MCP73838-FCI/MF BACA MCP73838T-FCI/MF BACA

MCP73838-FJI/MF BACB MCP73838T-FJI/MF BACB

MCP73838-NVI/MF BACC MCP73838T-NVI/MF BACC

Part Number(1)Marking

Code Part Number(1)Marking

Code

MCP73837-FCI/UN 837FCI MCP73837T-FCI/UN 837FCI

MCP73837-FJI/UN 837FJI MCP73837T-FJI/UN 837FJI

MCP73837-NVI/UN 837NVI MCP73837T-NVI/UN 837NVI

MCP73838-FCI/UN 838FCI MCP73838T-FCI/UN 838FCI

MCP73838-FJI/UN 838FJI MCP73838T-FJII/UN 838FJI

MCP73838-NVI/UN 838NVI MCP73838T-NVI/UN 838NVI

MCP73838-AMI/UN 838AMI MCP73838T-AMI/UN 838AMI

BABA

1539

256

837FCI

539256

Note 1: Consult Factory for Alternative Device Options.

2: Consult Factory for MSOP Package Availability.

(2)

 2007-2015 Microchip Technology Inc. DS20002071C-page 25

MCP73837/8