LTC4095
6
4095fa
PIN FUNCTIONS
BAT (Pin 1): Single Cell Li-Ion Battery Pin. Provides charge
current to the battery and regulates fi nal fl oat 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 specifi cation. 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
coeffi cient 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.
