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The MAX6399 is a small overvoltage and undervoltage
protection circuit. The device can monitor a DC-DC output
voltage and quickly disconnect the power source
from the DC-DC input load when an overvoltage condition
occurs. A power-OK output signals when the
DC-DC input voltage falls below an adjustable threshold.
This controller architecture provides the ability to
size the external n-channel MOSFET to meet specific
load current requirements.
When the DC-DC monitored output voltage is below the
user-adjustable overvoltage threshold, the GATE output
of the MAX6399 goes high to enhance the n-channel
MOSFET. The MAX6399 offers internal charge-pump
circuitry that allows the GATE voltage to be 10V above
the input voltage (VGS = 10V) to fully enhance the
external n-channel MOSFET, thus minimizing the drain-to-
source resistance.
When the monitored output voltage rises above the
user-adjusted overvoltage threshold, the GATE output
rapidly pulls low to shut off the MOSFET. The MOSFET
remains latched off until either the MAX6399 input
power or SHDN-bar input is cycled. The MAX6399 includes
a logic-low shutdown input that disables the GATE. An
internal overtemperature detector also disables the
gate when the MAX6399 temperature reaches the thermal-shutdown threshold.
The device operates over a wide supply voltage range
(5.75V to 72V) and is offered in a small TDFN package,
fully specified from -40°C to +125°C.
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