Datasheet

LTC4062
13
4062fb
APPLICATIO S I FOR ATIO
WUUU
charge the battery until the internal timer reaches 3 hours
(as set by C
TIMER
). During recharge cycles, the LTC4062
charges the battery until the internal timer reaches
1.5 hours. Figure 3 describes the operation of the LTC4062
charger when charge time termination is used.
Charge Current Termination
Connecting the TIMER pin to ground selects charge cur-
rent termination. With this method, the timer is disabled
and a resistor (R
DET
) must be connected from the I
DET
pin
to ground. I
DETECT
is programmed using the same equa-
tion stated in the previous section. The charge cycle
terminates when the charge current falls below I
DETECT
.
This condition is detected using an internal filtered com-
parator to monitor the I
DET
pin. When the I
DET
pin falls
below 100mV for longer than t
TERM
(typically 1.5ms),
charging is terminated.
When charging, transient loads on the BAT pin can cause
the I
DET
pin to fall below 100mV for short periods of time
before the DC current has dropped below the I
DETECT
+
V
CC
CHRG
PROG
I
DET
C
TIMER
0.1µF
V
IN
4062 F02
BAT
500mA
TIMER
R
DET
1k
R
PROG
2k
LTC4062
GND
C/5
Figure 2. Time Termination Mode.
The Charge Cycle Ends After 3 Hours
Figure 3. State Diagram of a Charge Cycle
Using Charge Time Termination
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
4062 F03
TRICKLE CHARGE MODE
1/10TH FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT < 4.1V
BAT > 4.1V
EN = 5V
OR
UVLO CONDITION
STANDBY MODE
NO CHARGE CURRENT
CHRG STATE: Hi-Z
SHUTDOWN MODE
I
CC
DROPS TO 20µA
CHRG STATE: Hi-Z
CHRG STATE: PULL-DOWN
DEFECTIVE BATTERY
FAULT MODE
NO CHARGE CURRENT
CHRG STATE: PULSING
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
EN = 0V
OR UVLO
CONDITION
STOPS