ADP2291

Rev. 0 | Page 14 of 20

TYPICAL APPLICATION CIRCUIT

A typical application circuit is shown in Figure 22. The circuit is

capable of a 750 mA charge current for an input voltage of 4.5 V

to 6 V. Higher input voltages can be used, but the increased

power dissipation of the pass device must be taken into account.

ADP2291

TIMER

ADJ

RS

200m

Ω

Q1

FZT549

D1

BAT1000

CTIMER

100nF

INPUT

4.6V–12V

+

IN

CHG

BAT

CIN

2.2

µF

GND

CS

DRV

COUT

10

µF

Figure 22. Typical Application Circuit

EOC TERMINATES CHARGING

In some applications, the charger is required to terminate

charging when the EOC threshold is reached. Automatic

charger restart is not desired. Adding components R1, C1, and

Q2 terminates charging when the CHG pin opens and prevents

further charging until the adapter is removed and reasserted.

ADP2291

TIMER

ADJ

RS

200m

Ω

Q1

FZT549

Q2

2N7002

D1

BAT1000

CTIMER

100nF

C1

100nF

INPUT

4.6V–12V

+

IN

CHG

BAT

CIN

2.2

µF

R1

500k

Ω

GND

CS

DRV

COUT

10

µF

LI-ION

CELL

Figure 23. Self-Termination Circuit

SELECTABLE CHARGE CURRENT

In applications where the charge current needs to be selectable,

use the circuit shown in Figure 24. This circuit allows a

processor to determine if the charge current needs to be

reduced due to an input source limitation or a different battery

capacity option, or simply to reduce the stress on the pass

transistor. R2 and Q2 allow the charge current to be selected

between HIGH—750 mA, and LOW—250 mA.

ADP2291

TIMER

ADJ

RS

200m

Ω

R2

100k

Ω

Q1

FZT549

Q2

2N7002

D1

BAT1000

CTIMER

100nF

INPUT

4.6V–12V

+

IN

CHG

BAT

CIN

2.2

µF

GND

CS

DRV

LOW/HIGH

COUT

10

µF

LI-ION

CELL

Figure 24. Selectable Charge Current Circuit

THERMAL PROTECTION

In applications where the overall size must be small or the input

voltage range is wide, adding thermal regulation is suggested.

This allows the charger to monitor the temperature of the pass

device and decrease the charge current as the temperature

increases. By adding a NTC thermistor to the ADJ pin it is

possible to accomplish this; however, care is still required to

ensure that the power dissipation of the pass device is not

exceeded.

ADP2291

TIMER

ADJ

RS

200m

Ω

Q1

FZT549

R1

470k

NTC LOCATED

NEAR Q1

R2

100k

D1

BAT1000

CTIMER

100nF

INPUT

4.6V–12V

+

IN

CHG

BAT

CIN

2.2

µF

GND

CS

DRV

COUT

10

µF

LI-ION

CELL

Figure 25. Thermal Regulation Circuit

Some suggested NTC thermistor suppliers are listed in Table 6.

Table 6. NTC Thermistor Manufacturers

Vendor

Part Number

Website

BetaTherm

SMD2500KJ435J

www.betatherm.com

Murata

NCP18WM474J

www.murata .com

Panasonic

ERTJ0EV474J

www.panasonic.com

Vishay

2322 615 1.474

www.vishay.com