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 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 user-adjustable 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.