ltc4414ems8-trpbf Linear Technology Corporation, ltc4414ems8-trpbf Datasheet - Page 10

• Manufacturer Part Number: ltc4414ems8-trpbf
• Description: 36v, Low Loss Powerpath Controller For Large Pfets
• Manufacturer: Linear Technology Corporation

LTC4414
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 3 illustrates an application circuit for microcontrol-
ler 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 LTC4414 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 available).
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
TYPICAL APPLICATIO S
10
MICROCONTROLLER
AUXILIARY POWER
SOURCE INPUT
Figure 3. Microcontroller Monitoring and Control
of Two Power Sources
*DRAIN-SOURCE DIODE OF MOSFET
SOURCE INPUT
PRIMARY
0.1µF
POWER
*
7
3
2
V
GND
CTL
P-CHANNEL MOSFETS
LTC4414
IN
P-CHANNEL MOSFETS
*
470k
SENSE
AUXILIARY
GATE
STAT
PRIMARY
6
8
1
U
*
4414 F03
OUT
*
R
and the load
LIMIT
OPTIONAL
ZENER
CLAMP
IF V
AN ISSUE
GS(MAX)
C
OUT
TO LOAD
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
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
transition 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
mended for load sharing.
High Current Power Supply Load Sharing
Figure 4 illustrates an application circuit for dual identical
power supply load sharing. The load will then be shared
between the two power supplies according to their source
impedances. The STAT pins provide information as to
which input is supplying the load current. This concept can
be expanded to more power inputs.
SUPPLY1
SUPPLY2
OUT
POWER
POWER
Figure 4. High Current Dual Power Supply Load Sharing
capacitance must be sized to hold up V
IN
7
3
2
7
3
2
*DRAIN-SOURCE DIODE OF MOSFET
Q1, Q2: SUB75P03-07
will help ensure this. If desired, this can be
V
GND
CTL
V
GND
CTL
LTC4414
IN
LTC4414
IN
SENSE
SENSE
GATE
GATE
STAT
STAT
IN
falls below V
6
8
1
6
8
1
*
*
LOAD
Q1
Q2
. This circuit is not recom-
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH POWER SUPPLIES
ARE SUPPLYING LOAD CURRENTS.
V
V
CC
CC
LOAD
47k
47k
IN
LOAD
to ensure that V
, it will turn on the
4414 F04
C
OUT
must stay up
LOAD
TO LOAD
STATUS
STATUS
until the
4414fc
IN