Datasheet

LTC4415
15
4415fa
Typical applicaTions
Load Sharing by Multiple Batteries and Automatic
Switchover to a Preferred Power Supply
(Such as a Wall Adapter)
An application circuit for dual battery load sharing with
automatic switchover to a wall adapter (when present)
is shown in Figure 8. In the absence of the wall adapter,
the higher voltage battery provides the load current until
it has discharged to the voltage of the other battery. The
load is then shared between the two batteries according
to their capacities, the higher capacity battery providing
proportionally higher current to the load unless limited
by its current limit.
When a wall adapter is applied, the output voltage rises
as the body diode of PFET MP1 conducts and both of the
ideal diode paths in the LTC4415 stop conducting due to
reverse turn-off. At this time, the wired-OR status signal
pulls up the gate voltage of NFET MN1, pulling down the
gate voltage of power PFET MP1, turning it on. The wired-OR
status signal indicates whether the wall adapter or either
of the two batteries is supplying the load current. The two
application circuits described in Figure 7 and Figure 8 can
be cascaded for dual battery charging and load sharing.
Microcontrolled Power Switch with Reverse Blocking,
Selectable Current Limit, Soft-Start and Monitoring
Figure 9 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller monitors the input supply voltages and
commands the LTC4415 through EN1/EN2 inputs.
Currents through the ideal diodes are monitored by the
microcontroller measuring CLIM1/CLIM2 pin voltages
using ADCs. The current limit can be adjusted for either
diode using an external FET as shown in this application
for diode 1 with MN1. The two ideal diode outputs are
connected together for power source ORing, or they may
feed different loads.
Parallel Diodes for Lower Resistance or Higher
Current Output
The two ideal diodes in the LTC4415 can be connected in
parallel as shown in Figure 10 to achieve a low resistance
PowerPath. The master enable input, ENABLE, turns on
diode 2. EN1 is tied to the output so that diode 1 conducts
only after the output has charged up (by diode 2 according
to its current limit setting). Diode 1 is disabled when the
Figure 8. Dual Battery Load Sharing with Automatic Switchover to a Wall Adapter
IDEAL
IDEAL
LTC4415
GND
EN1
470k
MN1
IRLML2402
CLIM1
CLIM2
STAT1
STAT
WARN1
WARN2
STAT2
EN2
IN2
BAT2
BAT1
IN1 OUT1
OUT2
470k
4.7µF
+
MP1 IRFHS9301
WALL ADAPTER
PV
IN1
PV
IN2
SW2
SW3
FB2
FB3
V
OUT1
LTC3521
SHDN2
SHDN1
1.0M
137k
68.1k
10µF
V
IN
4.7µH 4.7µH
V
OUT1
3.3V
0.8A
V
OUT2
1.8V
0.6A
100k
100k
10µF
4.7µH
V
OUT3
1.2V
0.6A
221k
4415 F08
SHDN3
PWM
SW1A
SW1B
FB1
PGOOD2
PGOOD1
PGOOD3PGND1A
PGND2GNDPGND1B
ON
OFF
PWM
BURST
+
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