MAX6398 Ver la hoja de datos (PDF) - Maxim Integrated
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MAX6398 Datasheet PDF : 18 Pages
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Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
GATE
IN
IN
OUT
R1
MAX6397
MAX6398 SET
GND
R2
Figure 6. Setting the MAX6397/MAX6398 Overvoltage Threshold
GATE
IN
IN
OUT
R1
MAX6397
SET MAX6398
R2
GND
Q1
VBATT
IN
GATE
MAX6397
MAX6398
OUT
GND
LOAD
VBATT
IN
GATE
LOAD
MAX6397
MAX6398
OUT
GND
(a)
(b)
Figure 7. Reverse Battery Protection Using a Diode or p-Channel MOSFET
Reverse-Battery Protection
Use a diode or p-channel MOSFET to protect the
MAX6397/MAX6398 during a reverse-battery insertion
(Figures 7a, 7b). Low p-channel MOSFET on-resistance
of 30mΩ or less yields a forward-voltage drop of only a
few millivolts (versus hundreds of millivolts for a diode,
Figure 7a) thus improving efficiency.
Connecting a positive battery voltage to the drain of Q1
(Figure 7b) produces forward bias in its body diode,
which clamps the source voltage one diode drop below
the drain voltage. When the source voltage exceeds
Q1’s threshold voltage, Q1 turns on. Once the FET is
on, the battery is fully connected to the system and can
deliver power to the device and the load.
An incorrectly inserted battery reverse-biases the FET’s
body diode. The gate remains at the ground potential.
The FET remains off and disconnects the reversed bat-
tery from the system. The zener diode and resistor com-
bination prevent damage to the p-channel MOSFET
during an overvoltage condition.
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