Latch-type comparator for fault capture and zero-cross detection
The Maxim Integrated MAX903CSA+T is a single comparator with a latch output — meaning once the output changes state, it holds that state until the latch is reset. This makes it useful for capturing fast overcurrent events or zero-crossing transitions in motor drives and power converters, where the fault pulse may disappear before a microcontroller can poll the pin. The output is TTL-compatible, so it drives 5 V logic inputs directly without a level shifter. Common-mode rejection is 82.5 dB typical, and power-supply rejection is 80 dB typical, so threshold accuracy holds up in noisy environments like switching power supplies or motor-drive boards where the supply rail carries ripple and the input common-mode voltage swings.
The supply range covers 5 V to 10 V single or ±2.5 V to ±5 V dual. On a 5 V-only board, the comparator runs directly from the same rail as the MCU. On a mixed-signal board with ±5 V analog supplies, it shares those rails without an extra regulator. Input bias current is 10 µA maximum at ±5 V, and quiescent current draws up to 4 mA, 3 mA, or 1.5 mA depending on the supply condition — not a low-power part, but fine for line-powered designs where a few milliamps are budgeted.