Datasheet

LTC4063
12
4063fc
applicaTions inForMaTion
When the charge current (I
BAT
) is greater than I
DETECT
, the
CHRG output is in its pull-down state. When the charger
enters constant-voltage mode operation and the charge
current falls below I
DETECT
, the CHRG output becomes
high impedance, indicating that the battery is almost
fully charged. The CHRG output will also become high
impedance once the charge time elapses. If the IDET pin
is not connected, the CHRG output remains in its pull-
down state until the charge time elapses and terminates
the charge cycle.
Figure 2 shows a charger circuit using charge time termi-
nation that is programmed to charge at 500mA. Once the
charge current drops below 100mA in constant-voltage
mode (as set by R
DET
), the CHRG output turns off the
LED. This indicates to the user that the battery is almost
fully charged and ready to use. The LTC4063 continues to
charge the battery until the internal timer reaches 3 hours
(as set by C
TIMER
). During recharge cycles, the LTC4063
charges the battery until the internal timer reaches 1.5
hours. Figure 3 describes the operation of the LTC4063
charger when Charge Time Termination is used.
+
V
CC
CHRG
PROG
IDET
C
TIMER
0.1µF
V
IN
4063 F02
BAT
500mA
TIMER
R
DET
1k
R
PROG
2k
LTC4063
GND
Figure 2. Charge Time Termination. The Charger
Automatically Shuts Off After 3 Hours
CHARGE MODE
FULL CURRENT
CHRG STATE:
PULL-DOWN IF I
BAT
> I
DETECT
Hi-Z IF I
BAT
< I
DETECT
CHARGE TIME
ELAPSES
1/4 CHARGE TIME
ELAPSES
BAT < 4.1V
4063 F03
TRICKLE CHARGE MODE
1/10 FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT < 4.1V
BAT > 4.1V
CHGEN = 5V
OR
UVLO CONDITION
STANDBY MODE
NO CHARGE CURRENT
CHRG STATE: Hi-Z
SHUTDOWN MODE
I
CC
DROPS TO 35µA
CHRG STATE: Hi-Z
CHRG STATE: PULL-DOWN
FAULT MODE
NO CHARGE CURRENT
CHRG STATE: SQUARE WAVE
RECHARGE MODE
FULL CURRENT
CHRG STATE:
PULL-DOWN IF I
BAT
> I
DETECT
Hi-Z IF I
BAT
< I
DETECT
1/2 CHARGE
TIME ELAPSES
POWER ON
CHGEN = 0V
OR UVLO
CONDITION
STOPS
Figure 3. State Diagram of a Charge Cycle Using Charge Time Termination