Datasheet

LTC4054L-4.2
10
4054l42fa
operaTion
Manual Shutdown
At any point in the charge cycle, the LTC4054L can be put
into shutdown mode by removing R
PROG
thus floating
the PROG pin. This reduces the battery drain current to
less than 2µA and the supply current to less than 50µA.
A new charge cycle can be initiated by reconnecting the
program resistor.
In manual shutdown, the CHRG pin is in a weak pull-down
state as long as V
CC
is high enough to exceed the UVLO
conditions. The CHRG pin is in a high impedance state
if the LTC4054L is in undervoltage lockout mode: either
V
CC
is within 100mV of the BAT pin voltage or insufficient
voltage is applied to the V
CC
pin.
Automatic Recharge
Once the charge cycle is terminated, the LTC4054L con-
tinuously monitors the voltage on the BAT pin using a
comparator with a 2ms filter time (t
RECHARGE
). A charge
cycle restarts when the battery voltage falls below 4.05V
(which corresponds to approximately 80% to 90% bat-
tery capacity). This ensures that the battery is kept at or
near a fully charged condition and eliminates the need
for periodic charge cycle initiations. CHRG output enters
a strong pull-down state during recharge cycles.