Datasheet
LTC4063
14
4063fc
applicaTions inForMaTion
Figure 5. State Diagram of a Charger Cycle Using User Termination
Figure 6. Two Circuits that Charge at 500mA
Full-Scale Current and Terminate at 50mA
CHARGE MODE
FULL CURRENT
4063 F05
TRICKLE CHARGE MODE
1/10 FULL CURRENT
BAT > 2.9V
BAT < 2.9V
2.9V < BAT
CHGEN = 5V
OR
UVLO CONDITION
SHUTDOWN MODE
I
CC
DROPS TO 35µA
CHRG STATE: Hi-Z
CHRG STATE: PULL-DOWN
POWER ON
CHGEN = 0V
OR UVLO
CONDITION
STOPS
CHRG STATE:
PULL-DOWN IF I
BAT
> I
DETECT
Hi-Z IF I
BAT
< I
DETECT
With User-Selectable Charge Termination, the SmartStart
feature is disabled; when the charger is powered on or
enabled, the LTC4063 automatically begins charging, re-
gardless of the battery voltage. Figure 5 describes charger
operation when User-Selectable Charge Termination is
used.
Programming
C/10 Current Detection/Termination
In most cases, an external resistor, R
DET
, is needed to set
the charge current detection threshold, I
DETECT
. However,
when setting I
DETECT
to be 1/10th of I
CHG
, the IDET pin
can be connected directly to the PROG pin. This reduces
the component count, as shown in Figure 6.
When PROG and IDET are connected in this way, the
full-scale charge current, I
CHG
, is programmed using a
different equation:
R
V
I
I
V
R
PROG
CHG
CHG
PROG
= =
500 500
,
Stability Considerations
The battery charger constant voltage mode feedback loop
is stable without any compensation provided a battery
is connected. However, a 1µF capacitor with a 1Ω series
resistor to GND is recommended at the BAT pin to keep
ripple voltage low when the battery is disconnected.
When the charger is in constant current mode, the PROG
pin is in the feedback loop, not the battery. The constant
current stability is affected by the impedance at the PROG
pin. With no additional capacitance on the PROG pin, the
charger is stable with program resistor values as high as
10k; however, additional capacitance on this node reduces
the maximum allowed program resistor.
For the LDO regulator, a capacitor (C
OUT
) must be connected
from OUT to GND to ensure regulator loop stability. It is
recommended that low ESR capacitors be used for C
OUT
to reduce noise on the output of the linear regulator. C
OUT
must be ≥2µF for best performance.
+
V
CC
PROG
IDET
V
IN
BAT
500mA
TIMER
R
DET
2k
R
PROG
2k
LTC4063
GND
+
V
CC
PROG
IDET
V
IN
4063 F06
BAT
500mA
TIMER
R
PROG
1k
LTC4063
GND