LTC4055 Linear Technology, LTC4055 Datasheet - Page 9

• Manufacturer Part Number: LTC4055
• Description: USB Power Controller and Li-Ion Linear Charger
• Manufacturer: Linear Technology

PI FU CTIO S
TIMER (Pin 12): Timer Capacitor. Placing a capacitor
C
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.
TIMER
U
t
TIMER
to GND sets the timer period. The timer period is:
(
U
Hours
)
U
C
TIMER
0 1
•
.
R
PROG
F
•
100
•
3
k
Hours
V
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
(Cold, 0 C) or below 0.29 • V
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
V
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 NTC functions.
Exposed Pad (Pin 17): Ground. The Exposed Pad must be
soldered to a good thermally conductive PCB ground.
NTC
VNTC
NTC
(Pin 15): Output Bias Voltage for NTC. A resistor
, the timer continues where it left off and charging is
. When the voltage on this pin is above 0.74 • V
VNTC
(Hot, 50 C) the timer is
VNTC
LTC4055
and 0.29 •
VNTC
4055p
9