LTC4095

6

4095fa

PIN FUNCTIONS

BAT (Pin 1): Single Cell Li-Ion Battery Pin. Provides charge

current to the battery and regulates final float voltage to

4.2V.

GND (Pin 2): Ground

⎯C⎯H⎯R⎯G (Pin 3): Open-Drain Charge Status Output. The

⎯C⎯H⎯R⎯G pin indicates the status of the battery charger. Four

possible states are represented by ⎯C⎯H⎯R⎯G: charging, not

charging (i.e., the charge current is less than 1/10th of the

full-scale charge current), unresponsive battery (i.e., the

battery voltage remains below 2.9V after 1/2 hour of charg-

ing) and battery temperature out of range. ⎯C⎯H⎯R⎯G requires

a pull-up resistor and/or LED to provide indication.

SUSP (Pin 4): Suspend Mode Input. A voltage greater

than 1.2V on the SUSP pin puts the LTC4095 into suspend

mode, disables the charger and resets the termination

timer. A weak pull-down current is internally applied to

this pin to ensure it is low when the input is not being

driven externally.

HPWR (Pin 5): High Power Select Input. A voltage greater

than 1.2V on the HPWR pin will set the charge current to

100% of its programmed value. A voltage less than 0.4V

on the pin will set the charge current to 20% of its pro-

grammed value. When used with a 1.74k PROG resistor

this pin can toggle between low power and high power

modes per USB specification. A weak pull-down current

is internally applied to this pin to ensure it is low when

the input is not being driven externally.

NTC (Pin 6): Input to the NTC Thermistor Monitoring

Circuit. The NTC pin connects to a negative temperature

coefficient thermistor which is typically co-packaged with

the battery pack to determine if the battery is too hot or

too cold to charge. If the battery temperature is out of

range, charging is paused until the battery temperature

re-enters the valid range. A low drift bias resistor is re-

quired from IN to NTC and a thermistor is required from

NTC to ground. To disable the NTC function, the NTC pin

should be grounded.

PROG (Pin 7): Charge Current Program and Charge Current

Monitor Pin. Charge current is programmed by connect-

ing a resistor from PROG to ground. When charging in

constant-current mode, the PROG pin servos to 1V if the

HPWR pin is pulled high, or 200mV if the HPWR pin is

pulled low. The voltage on this pin always represents the

battery current through the following formula:

I

PROG

R

BAT

PROG

=

•800

IN (Pin 8): Input Supply Voltage. This pin provides power

to the battery charger and should be bypassed with at least

a 1µF capacitor. IN can range from 4.3V to 5.5V.

Exposed Pad (Pin 9): Ground. The exposed package pad

is ground and must be soldered to the PCB ground for

proper functionality and for maximum heat transfer.