Switch-Mode 1-Cell Li+ Chargers

8

_______________________________________________________________________________________

Pin Description

PIN

NAME

FUNCTION

1

CHG

Charge Status LED Driver. Open-drain LED driver sinks 10mA when the MAX1925/MAX1926 are charging.

CHG also blinks at a 0.5Hz rate during fault states (see the Timing section). High impedance when charger is

in shutdown. See Tables 1 and 2.

2EN

Enable. Drive EN high to enable charger. Logic level input for normal ON/OFF control. In the MAX1926 EN is

internally pulled up to 3V with a 300kΩ resistor.

3

THRM

Thermistor Input. Monitors external thermistor (10k

Ω at +25°C). When external temperature is lower than 0°C

or above +50

°C, charging stops and the charger enters fault mode. Charging resumes when the temperature

returns to normal. During a temperature fault the MAX1926 blinks the CHG output, while MAX1925 CHG

remains off (high).

4

ACON

Power-OK Indicator Output. Open-drain output goes low when AC adapter power is valid. See Table 2 for

ACON states.

5CT

Timing Capacitor Connection. Connect timer cap to program full-charge safety timeout interval and

Prequal2 Timer: Full Timer/17 (10.67 min)

Prequal1 Timer: Full Timer/1088 (10s)

6

CS

Charge-Current Sense Input. 142mV nominal regulation threshold. CS is high impedance during shutdown.

7

BATT

Battery-Sense Input. Also negative side of charge-current sense. BATT is high impedance during shutdown.

8

GND

Ground

9

PGND

Power Ground

10

EXT

PMOS Gate-Driver Output. Drives gate of external PMOS switching transistor from IN to GND. When using the

11

INP

Supply Voltage Input

12

IN

Supply-Sense Input. Connect IN to INP.