Datasheet

12
LTC4065/LTC4065A
4065fb
Transconductance amplifier, TA, limits the die tempera-
ture to approximately 115°C when in constant-tempera-
ture mode. Diode D3 ensures that TA does not affect the
charge current when the die temperature is below approxi-
mately 115°C. The PROG pin voltage continues to give an
indication of the charge current.
In typical operation, the charge cycle begins in constant-
current mode with the current delivered to the battery
equal to 1000V/R
PROG
. If the power dissipation of the
LTC4065/LTC4065A results in the junction temperature
approaching 115°C, the amplifier (TA) will begin decreas-
ing the charge current to limit the die temperature to
approximately 115°C. As the battery voltage rises, the
LTC4065/LTC4065A either return to constant-current mode
or enter constant-voltage mode straight from constant-
temperature mode. Regardless of mode, the voltage at
the PROG pin is proportional to the current delivered to
the battery.
OPERATIO
U
IS EN > SHUTDOWN
THRESHOLD?
ENABLE
CHRG HIGH IMPEDANCE
SHUTDOWN MODE
IF V
CC
> 3.6V AND
V
CC
> V
BAT
+ 80mV?
UVLO UVLO MODE
1/10 FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
TRICKLE CHARGE MODE
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
FAST CHARGE MODE
IS V
BAT
< 2.9V?
DEFECTIVE BATTERY
IS V
BAT
< 4.1V?
RECHARGE
NO CHARGE CURRENT
CHRG PULSES (2Hz)
BAD BATTERY MODE
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
RECHARGE MODE
NO CHARGE CURRENT
CHRG HIGH IMPEDANCE
STANDBY MODE
CHRG HIGH IMPEDANCE
NO
YES
YES YES
NO
NO
4065 F02
V
BAT
≤ 2.9V
1/4 CHARGE CYCLE
(1.125 HOURS)
V
CC
< 3V
OR
EN > SHDN
THRESHOLD
CHARGE CYCLE
(4.5 HOURS)
1/2 CHARGE CYCLE
(2.25 HOURS)
2.9V < V
BAT
< 4.1V V
BAT
> 4.1V
YES
NO
POWER
ON
Figure 2. State Diagram of LTC4065 Operation