Datasheet

MAX1925/MAX1926
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 (10kΩ 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
prequalification fault times. Timeouts with C
CT
= 100nF are:
Full Timer (t
FULLCHG
): 3 hours—If FASTCHG is not completed within this time a fault is asserted.
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
MAX1926, ensure that the MOSFET V
GS
rating is greater than V
IN
.
11 INP Supply Voltage Input
12 IN Supply-Sense Input. Connect IN to INP.