Datasheet

LTC4063
13
4063fc
applicaTions inForMaTion
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 IDET
pin to ground. I
DETECT
is programmed using the same
equation stated in the previous section (repeated here
for convenience):
I
R
R
I
V
R
or
R
V
I
DETECT
PROG
DET
CHG
DET
DET
DE
= =
=
10
100
100
•
TTECT
The charge cycle terminates when the charge current falls
below I
DETECT
. This condition is detected using an internal,
filtered comparator to monitor the IDET pin. When the
IDET 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 IDET pin to fall below 100mV for short periods of
time before the DC current has dropped below the I
DETECT
threshold. The 1.5ms filter time (t
TERM
) on the internal
comparator ensures that transient loads of this nature do
not result in premature charge cycle termination. Once the
average charge current drops below I
DETECT
, the charger
terminates the charge cycle.
The CHRG output is in its pull-down state when charging
and in its high impedance state once charging has stopped.
Figure 4 describes the operation of the LTC4063 charger
when charge current termination is used.
User
-Selectable
Charge Termination
Connecting the TIMER pin to VCC selects User-Select-
able Charge Termination, in which all internal termination
features are disabled. The charge cycle continues indefi-
nitely until the charger is shut down through the CHGEN
pin. The IDET pin programs the behavior of the CHRG
output in the same manner as when using Charge Time
Termination. Specifically, 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 charged. If the IDET pin is not connected,
the CHRG output remains in its pull-down state until the
charger is shut down.
CHARGE MODE
FULL CURRENT
I
BAT
< I
DETECT
IN VOLTAGE MODE
4063 F04
TRICKLE CHARGE MODE
1/10 FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT < 4.1V
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
CHRG STATE: PULL-DOWN
POWER ON
CHGEN = 0V
OR UVLO
CONDITION
STOPS
Figure 4. State Diagram of a Charge Cycle Using Charge Current Termination