Power Electronics

Overvoltage Protectors Target Automotive Designs

From Maxim Integrated Products, the MAX6397/MAX6398/MAX6399 overvoltage protectors are designed for systems with high transient voltages, such as those encountered in automotive and industrial applications.

The MAX6397/MAX6398/MAX6399 operates from 5.75 V to 72 V. The parts can be configured either as a switch controller that turns off an external n-channel switch during an overvoltage condition, or as a voltage limiter that regulates the output to allow continuous operation. An adjustable threshold allows two external resistors to set the overvoltage threshold level.

An internal charge pump ensures that the n-channel switch is fully enhanced during normal operating mode. In the switch-controller mode, the n-channel MOSFET is quickly shut off as the MOSFET's gate is quickly pulled down through an internal current source. In the voltage-limiting mode, the MOSFET is turned on and off to maintain a regulated voltage at the output.

These devices provide the necessary protection and reduce system cost by allowing use of lower input-voltage dc-dc regulators.

The MAX6397 has an independent always-on linear regulator that can deliver up to 100-mA output current with four fixed-output options of 5 V, 3.3 V, 2.5 V and 1.8 V. This device also features a power-good indicator.

The MAX6399 offers both an undervoltage and overvoltage threshold with a power-good indicator. An overvoltage latch mode keeps the n-channel MOSFET off until the power is recycled or the shutdown input is toggled. Other MAX6399 features include a shutdown input for manually shutting off the n-channel switch and thermal shutdown protection.

All three devices are offered in a small, 3-mm × 3-mm TDFN package and are fully specified from the -40°C to +125°C. Prices start at $1.23 each in lots of 1000. A preliminary datasheet for this product is available at www.maxim-ic.com/PRGraphics/PRPDF/MAX6397DS.pdf.

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