LTC4055-1_15 Datasheet, PDF (9/24 Pages) Linear Technology – USB Power Controller and Li-Ion Charger

LTC4055/LTC4055-1
PIN FUNCTIONS
TIMER (Pin 12): Timer Capacitor. Placing a capacitor C_TIMER
to GND sets the timer period. The timer period is:
t_TIMER(Hours)
=
C_TIMER • R_PROG • 3 Hours
0.1μF • 100k
Charge time is increased as charge current is reduced due
to input voltage regulation, load current and current limit
selection (HPWR).
Shorting the TIMER pin to GND disables the battery
charging functions.
ACPR (Pin 13): Wall Adapter Present Output. Active low
open-drain output pin. A low on this pin indicates that the
wall adapter input comparator has had its input pulled
above the input threshold and power is present on IN1/IN2
or OUT (i.e., above UVLO threshold).
CHRG (Pin 14): Open-Drain Charge Status Output. When
the battery is being charged, the CHRG pin is pulled low
by an internal N-channel MOSFET. When the timer runs
out or the input supply or output supply is removed, the
CHRG pin is forced to a high impedance state.
V_NTC (Pin 15): Output Bias Voltage for NTC. A resistor
from this pin to the NTC pin will set up the bias for an
NTC thermistor.
NTC (Pin 16): Input to the NTC Thermistor Monitoring
Circuits. Under normal operation, tie a thermistor from
the NTC pin to ground and a resistor of equal value from
NTC to V_NTC. When the voltage on this pin is above 0.74
• V_VNTC (Cold, 0°C) or below 0.29 • V_VNTC (Hot, 50°C)
the timer is suspended, but not cleared, the charging is
disabled and the CHRG pin remains in its former state.
When the voltage on NTC comes back between 0.74 •
V_VNTC and 0.29 • V_VNTC, the timer continues where it
left off and charging is re-enabled if the battery voltage
is below the recharge threshold. There is approximately
3°C of temperature hysteresis associated with each of the
input comparators.
If the NTC function is not to be used, connect the NTC to
ground. This will disable all of the LTC4055/LTC4055-1
NTC functions.
Exposed Pad (Pin 17): Ground. The Exposed Pad must be
soldered to a good thermally conductive PCB ground.
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