Datasheet

LTC4412
12
4412fb
For more information www.linear.com/LTC4412
Typical applicaTions
Multiple Battery Charging
Figure 6 illustrates an application circuit for automatic
dual battery charging from a single charger. Whichever
battery has the lower voltage will receive the charging
current until both battery voltages are equal, then both
will be charged. When both are charged simultaneously,
the higher capacity battery will get proportionally higher
current from the charger. For Li-Ion batteries, both batteries
will achieve the float voltage minus the forward regulation
voltage of 20mV. This concept can apply to more than
two batteries. The STAT pins provide information as to
which batteries are being charged. For intelligent control,
the CTL pin input can be used with a microcontroller and
back-to-back MOSFETs as shown in Figure 4. This allows
complete control for disconnection of the charger from
either battery.
High Side Power Switch
Figure 7 illustrates an application circuit for a logic con-
trolled high
side power switch.
When the CTL pin is a logical
low, the LTC4412 will turn on the MOSFET. Because the
SENSE pin is grounded, the LTC4412 will apply maximum
clamped gate drive voltage to the MOSFET. When the CTL
pin is a logical high, the LTC4412 will turn off the MOSFET
by pulling its
gate voltage up to the supply input voltage
and thus deny
power to the load. The MOSFET is con-
nected with
its source connected to the power source. This
disables the drain-sour
ce diode from supplying voltage
to the load when the MOSFET is off. Note that if the load
is powered from another source, then the drain-source
diode can forward bias and deliver current to the power
supply connected to the V
IN
pin.
Figure 6. Automatic Dual Battery Charging
from Single Charging Source
Figure 7. Logic Controlled High Side Power Switch
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412
TO LOAD OR
PowerPath
CONTROLLER
TO LOAD OR
PowerPath
CONTROLLER
STATUS IS HIGH
WHEN BAT1 IS
CHARGING
STATUS IS HIGH
WHEN BAT2 IS
CHARGING
470k
4412 F06
V
CC
*
*
BAT1
BATTERY
CHARGER
INPUT
470k
V
CC
BAT2
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412
*DRAIN-SOURCE DIODE OF MOSFET
0.1µF
V
IN
GND
CTL
SENSE
GATE
STAT
1
2
3
6
5
4
LTC4412
P-CHANNEL
MOSFET
SUPPLY
INPUT
LOGIC
INPUT
C
OUT
*
TO LOAD
4412 F07
*DRAIN-SOURCE DIODE OF MOSFET
0.1µF
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