LTC4412IS6#PBF Linear Technology, LTC4412IS6#PBF Datasheet - Page 10
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LTC4412IS6#PBF
Manufacturer Part Number
LTC4412IS6#PBF
Description
LEAD FREE LOW LOSS POWERPATH CONTROLLER
Manufacturer
Linear Technology
Datasheet
1.LTC4412IS6PBF.pdf
(12 pages)
Specifications of LTC4412IS6#PBF
Rohs Compliant
YES
Leaded Process Compatible
Yes
Peak Reflow Compatible (260 C)
Yes
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LTC4412
This is due to the SENSE pin voltage rising above the
battery voltage and turning off the MOSFET before the
Schottky diode turns on. The factors that determine the
magnitude of the voltage droop are the auxiliary input rise
time, the type of diode used, the value of C
current.
Ideal Diode Control with a Microcontroller
Figure 4 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller’s analog inputs, perhaps with the aid of
a resistor voltage divider, monitors each supply input and
commands the LTC4412 through the CTL input. Back-to-
back MOSFETs are used so that the drain-source diode
will not power the load when the MOSFET is turned off
(dual MOSFETs in one package are commercially avail-
able).
With a logical low input on the CTL pin, the primary input
supplies power to the load regardless of the auxiliary
voltage. When CTL is switched high, the auxiliary input
will power the load whether or not it is higher or lower
than the primary power voltage. Once the auxiliary is on,
the primary power can be removed and the auxiliary will
continue to power the load. Only when the primary
voltage is higher than the auxiliary voltage will taking CTL
low switch back to the primary power, otherwise the
TYPICAL APPLICATIO S
10
MICROCONTROLLER
AUXILIARY POWER
Figure 4. Microcontroller Monitoring and Control
of Two Power Sources
SOURCE INPUT
*DRAIN-SOURCE DIODE OF MOSFET
SOURCE INPUT
0.1μF
PRIMARY
POWER
1
2
3
*
P-CHANNEL MOSFETS
V
GND
CTL
LTC4412
IN
P-CHANNEL MOSFETS
*
SENSE
AUXILIARY
GATE
STAT
PRIMARY
470k
6
5
4
U
*
*
4412 F04
OUT
and the load
C
OUT
TO LOAD
auxiliary stays connected. When the primary power is
disconnected and V
auxiliary MOSFET if CTL is low, but V
long enough for the MOSFET to turn on. At a minimum,
C
transistion between the sets of MOSFETs is complete.
Sufficient capacitance on the load and low or no capaci-
tance on V
avoided by use of a capacitor on V
falls more slowly than V
Load Sharing
Figure 5 illustrates an application circuit for dual battery
load sharing with automatic switchover of load from
batteries to wall adapter. Whichever battery can supply the
higher voltage will provide the load current until it is
discharged to the voltage of the other battery. The load will
then be shared between the two batteries according to the
capacity of each battery. The higher capacity battery will
provide proportionally higher current to the load. When a
wall adapter input is applied, both MOSFETs will turn off
and no load current will be drawn from the batteries. The
STAT pins provide information as to which input is supply-
ing the load current. This concept can be expanded to
more power inputs.
ADAPTER
OUT
BAT1
BAT2
INPUT
WALL
capacitance must be sized to hold up V
Figure 5. Dual Battery Load Sharing with Automatic
Switchover of Load from Batteries to Wall Adapter
IN
1
2
3
1
2
3
*DRAIN-SOURCE DIODE OF MOSFET
will help ensure this. If desired, this can be
V
GND
CTL
V
GND
CTL
LTC4412
IN
LTC4412
IN
SENSE
SENSE
GATE
GATE
STAT
STAT
IN
falls below V
6
5
4
6
5
4
*
*
LOAD
.
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH BATTERIES ARE
SUPPLYING LOAD CURRENTS. WHEN
BOTH STATUS LINES ARE LOW THEN
WALL ADAPTER IS PRESENT
V
V
CC
CC
LOAD
470k
470k
IN
LOAD
to ensure that V
, it will turn on the
4412 F05
C
OUT
must stay up
LOAD
TO LOAD
STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
LOAD CURRENT
STATUS IS HIGH
WHEN BAT2 IS
SUPPLYING
LOAD CURRENT
until the
4412fa
IN