The MAX6495–MAX6499 is a family of small, low-current, overvoltage-protection circuits for high-voltage transient systems such as those found in automotive and industrial applications. These devices monitor the input voltage and control an external nMOSFET switch to isolate the load at the output during an input overvoltage condition. The MAX6495–MAX6499 operate over a wide supply voltage range from +5.5V to +72V.
The gate of the nMOSFET is driven high while the monitored input is below the user-adjustable overvoltage threshold. An integrated charge-pump circuit provides a 10V gate-to-source voltage to fully enhance the nMOSFET. When the input voltage exceeds the user-adjusted overvoltage threshold, the gate of the MOSFET is quickly pulled low, disconnecting the load from the input. 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 (MAX6495/MAX6496/MAX6499).
The MAX6496 supports lower input voltages and reduces power loss by replacing the external reverse battery diode with an external series pMOSFET. The MAX6496 generates the proper bias voltage to ensure that the pMOSFET is on during normal operations. The gate-to-source voltage is clamped during load-dump conditions, and the p-channel MOSFET is off during reverse-battery conditions.
The MAX6497/MAX6498 feature an open-drain, undedicated comparator that notifies the system if the output falls below the programmed threshold. The MAX6497 keeps the MOSFET switch latched off until either the input power or the active-low SHDN pin is cycled. The MAX6498 will autoretry when VOVSET falls below 130mV.
These devices are available in small, thermally enhanced, 6-pin and 8-pin TDFN packages and are fully specified from -40°C to +125°C.
