The STMicroelectronics SR1CARU is a single-channel reset timer from the Smart Reset™ family, designed to hold a microcontroller or other logic device in reset until the supply rail has stabilised and a user-programmable timeout has elapsed. Its active-low, open-drain output directly drives the /RESET pin of most MCUs without needing a level translator. The adjustable threshold and timeout make it a flexible choice for designs where the power-up sequence or brown-out recovery window isn't fixed at the layout stage.
Unlike fixed-threshold supervisors (e.g. the STM809 series with a 140 ms timeout), the SR1CARU lets you set both the voltage trip point and the reset release delay with external components. That matters when your power rail has a slow ramp or you need a longer hold-off to let an external sensor or transceiver initialise before the MCU starts executing code. One external capacitor sets the timeout; the threshold is set by a resistor divider on the sense input. This configurability reduces the number of unique supervisor SKUs on the BOM — one part covers multiple rail voltages and timing requirements across a product family.
Active-low open-drain output
The open-drain output pulls low when the monitored voltage drops below the threshold or during power-up. It releases after the timeout expires.