The MAX6397/MAX6398 are small, high-voltage overvoltage protection circuits. These devices disconnect the output load or limit the output voltage during an input overvoltage condition. These devices are ideal for applications that must survive high-voltage transients such as those found in automotive and industrial applications.The MAX6397/MAX6398 monitor the input or output voltages and control an external n-channel MOSFET to
isolate or limit the load from overvoltage transient energy.
When the monitored input voltage is below the useradjustable
overvoltage threshold, the external n-channel
MOSFET is turned on by the GATE output. In this mode,
the internal charge pump fully enhances the n-channel
MOSFET with a 10V gate-to-source voltage.
When the input voltage exceeds the overvoltage threshold,
the protection can disconnect the load from the
input by quickly forcing the GATE output low. In some
applications, disconnecting the output from the load is
not desirable. In these cases, the protection circuit can
be configured to act as a voltage limiter where the
GATE output sawtooths to limit the voltage to the load.
The MAX6397 also offers an always-on linear regulator
that is capable of delivering up to 100mA of output
current. This high-voltage linear regulator consumes
only 37μA of quiescent current.
The regulator is offered with output options of 5V, 3.3V,
2.5V, or 1.8V. An open-drain, power-good output (POK)
asserts when the regulator output falls below 92.5% or
87.5% of its nominal voltage.The MAX6397/MAX6398 include internal thermal-shutdown
protection, disabling the external MOSFET and linear regulator if the chip reaches overtemperature conditions. The devices operate over a wide 5.5V to 72V supply voltage range, are available in small TDFN packages, and are fully specified from -40°C to +125°C.