Overvoltage Protection Switch/Limiter Controllers Operate Up to 72V

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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.
MAX6397, MAX6398: Typical Operating Circuit MAX6397, MAX6398: Typical Operating Circuit Enlarge+

Key Features

  • 5.5V to 72V Wide Supply Voltage Range
  • Overvoltage Protection Controllers Allow User to Size External n-Channel MOSFETs
  • Internal Charge-Pump Circuit Ensures MOSFET Gate-to-Source Enhancement for Low RDS(ON) Performance
  • Disconnect or Limit Output from Input During Overvoltage Conditions
  • Adjustable Overvoltage Threshold
  • Thermal-Shutdown Protection
  • Always-On, Low-Current (37µA) Linear Regulator Sources Up to 100mA (MAX6397)
  • Fully Specified from -40°C to +125°C (TJ)
  • Small, Thermally Enhanced 3mm x 3mm TDFN Package


  • FireWire®
  • Industrial
  • Notebook Computers
  • Wall Cube Power Devices

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX6397EVKIT: Evaluation Kit for the MAX6397
Product Reliability Reports: MAX6398.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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