Flexible Fault Protection

文章摘要：An internal charge pump generates controlled gate drive for an external n-channel MOSFET power switch (Q1). Following a fault condition, U1 latches Q1 off until cleared by an external-reset signal. To indicate fault conditions, connect an LED (or other fault indicator such as an audible alarm) to U1

Flexible Fault Protection,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com
An internal charge pump generates controlled gate drive for an external n-channel MOSFET power switch (Q1). Following a fault condition, U1 latches Q1 off until cleared by an external-reset signal. To indicate fault conditions, connect an LED (or other fault indicator such as an audible alarm) to U1's open-drain status output (STAT). After a fault is detected, you can reset U1 by pulsing its ON pin low for 20µS minimum.

The switch debouncer (U2) has inputs protected to ±15kV for ESD and to ±25V for circuit faults. Its input (shown connected to a normally-closed pushbutton switch) can clear a fault on U1 or provide a manual reset. An internal pull-up to Vcc eliminates the need for an external pull-up resistor. Replacing the pushbutton switch with an interlock or SPST switch provides a power-disconnect signal, which can implement a chassis-intrusion interlock, or allow a technician to power-down the unit before swapping circuit cards. Because U2's push-pull output cannot be directly OR-connected with other signals connected to U1's ON pin, Q2 is added to create an OR-able open-drain connection.

A temperature switch (U3) adds thermal protection, and its open-drain output can be connected either directly (wire-OR'd) to other signals on U1's ON pin, or separately, back to the microprocessor. With its TO220 package option, U3 can be bolted to a heat sink, or surface-mounted (SOT23 option) close to known heat-generating sources such as R1, Q1, or the main load. In this circuit U3 provides circuit protection by issuing a power-disconnect signal when the circuit temperature becomes critical. A low-power linear regulator (U4) provides 5V to the low-voltage components U2 and U3, but U4 is not meant to provide system power to the load.

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