Datasheet
LTC4228-1/LTC4228-2
18
422812f
applicaTions inForMaTion
goes high, allowing ON2 to turn on M
H2
and connect the
INPUT 2 to the output. Diode D1 ensures that ON2 remains
above 0.6V while in the off state so that when ON2 goes
high, M
H2
is turned on immediately without invoking the
100ms turn-on delay. When INPUT 1 returns to a viable
voltage, M
H1
turns on and M
H2
turns off. The ideal diode
MOSFETs M
D1
and M
D2
prevent backfeeding of one input
to the other under any condition.
Additional Applications
In most applications, the two external MOSFETs are con-
figured with the MOSFET on the supply side as the ideal
diode and the MOSFET on the load side as the Hot Swap
control. But for some applications, the arrangement of the
MOSFETs for the ideal diode and the Hot Swap control may
be reversed as shown in Figure 9. The Hot Swap MOSFET
is placed on the supply side and the ideal diode MOSFET
on the load side with the source terminals connected to-
gether. If this configuration is operated with 12V supplies,
the gate-to-source breakdown voltage of the MOSFETs
can be exceeded when the input or output is connected
to ground as the LTC4228’s internal 12V clamps only limit
the DGATE-to-IN and HGATE-to-OUT pin voltages. Choose
a MOSFET whose gate-to-source breakdown voltage is
rated for 25V or more as 24V voltage can appear across
the GATE and SOURCE pins of the MOSFET during an
input or output short. As shown in Figure 9, if a MOSFET
with a lower rated gate-to-source breakdown voltage is
chosen, an external Zener diode clamp is required between
the GATE and SOURCE pins of the MOSFET to prevent it
from breaking down.
Figure 8. 2-Channel Power Prioritizer
CPO1
ON1
EN1
ON2
EN2
INTV
CC
GND
C
CP1
0.1µF
C1
0.1µF
C
F1
0.1µF
C
HG1
33nF
C
L
470µF
C
T2
0.1µF
Z1
SMAJ13A
INPUT 1
INPUT 2
5V
PRIMARY
SUPPLY
12V
BACKUP
SUPPLY
C
CP2
0.1µF
C
T1
0.1µF
IN1 SENSE1
–
SENSE1
+
DGATE1
M
D1
SiR466DP
M
H1
SiR466DP
LTC4228
R
S1
0.006Ω
M
D2
SiR466DP
M
H2
SiR466DP
R
S2
0.006Ω
R3
3.92k
D1
LS4148
HGATE1
R
H1
10Ω
R
HG1
47Ω
V
OUT
5A
OUT1
CPO2 IN2 SENSE2
–
SENSE2
+
DGATE2 HGATE2 OUT2
422812 F08
STATUS1
FAULT1
PWRGD2
FAULT2
STATUS2
Z2
SMAJ13A
R4
41.2k
R2
49.9k
R1
20k
PWRGD1
TMR1
TMR2
+
+