MAX8903A–E/G/H/J/N/Y

2A 1-Cell Li+ DC-DC Chargers

for USB and Adapter Power

12

Maxim Integrated

Pin Description (continued)

PIN

NAME

FUNCTION

13

ISET

The prequal charge current is 10% of the fast-charge current.

14

CEN

Charger Enable Input. Connect

CEN to GND to enable battery charging when a valid source is connected

at DC or USB. Connect to VL, or drive high to disable battery charging.

15

USUS

USB Suspend Input. Drive USUS logic-high to enter USB suspend mode, lowering USB current to 115µA,

and internally shorting SYS to BAT.

16

THM

Thermistor Input. Connect a negative temperature coefficient (NTC) thermistor from THM to GND.

Connect a resistor equal to the thermistor +25°C resistance from THM to VL. Charging is suspended

when the thermistor is outside the hot and cold limits. Connect THM to GND to disable the thermistor

temperature sensor.

17

USB

USB Power Input. USB is capable of delivering 100mA or 500mA to SYS as set by the IUSB logic input.

Connect a 4.7µF ceramic capacitor from USB to GND.

18

FLT

Fault Output. Active-low, open-drain output pulls low when the battery timer expires before prequal or

fast-charge completes.

19

UOK

USB Power-OK Output. Active-low, open-drain output pulls low when a valid input is detected at USB.

UOK is still valid when the charger is disabled (CEN high).

20, 21

BAT

Battery Connection. Connect to a single-cell Li+ battery. The battery charges from SYS when a valid

source is present at DC or USB. BAT powers SYS when neither DC nor USB power is present, or when the

SYS load exceeds the input current limit. Both BAT pins must be connected together externally.

22

CHG

Charger Status Output. Active-low, open-drain output pulls low when the battery is in fast-charge or

prequal. Otherwise,

CHG is high impedance.

23, 24

SYS

System Supply Output. SYS connects to BAT through an internal 50m

Ω system load switch when DC or

USB are invalid, or when the SYS load is greater than the input current limit.

exceeds the DC or USB current limit, SYS is regulated to 50mV below BAT, and both the powered input

and the battery service SYS.

Bypass SYS to GND with an X5R or X7R ceramic capacitor. See Table 6 for the minimum recommended

25, 26

CS

70m

Ω Current-Sense Input. Connect the step-down inductor from LX to CS. When the step-down

regulator is on, there is a 70m

Ω current-sense MOSFET from CS to SYS. When the step-down regulator is

off, the internal CS MOSFET turns off to block current from SYS back to DC.

27, 28

LX

Inductor Connection. Connect the inductor between LX and CS. Both LX pins must be connected together

externally.

—EP

Exposed Pad. Connect the exposed pad to GND. Connecting the exposed pad does not remove the

requirement for proper ground connections to the appropriate pins.