Dual-voltage reset timer for processor power sequencing
The Texas Instruments TPS3421EGDRYT is a reset timer IC that monitors two supply voltages and asserts an active-low, open-drain reset output when either rail falls below the programmed threshold. The reset output remains low for a minimum of 320 ms after both voltages return within tolerance, giving the downstream processor or FPGA time to complete its initialization sequence. The threshold voltage is adjustable via external resistors, so the part can be set to trip at any voltage the designer chooses — useful for non-standard rails or when precise margin control is needed.
320 ms reset timeout — what it buys the system
The 320 ms minimum reset pulse width covers the power-on reset delay of most MCUs, FPGAs, and SoCs. Because the output is open drain, multiple reset sources (this timer, a manual reset button, a watchdog) can be wire-ORed to the same reset line. Just add a pull-up resistor to the processor's supply rail.
Package and footprint for tight PCB layouts
The TPS3421EGDRYT comes in a 6-UFDFN package with a 1.45 mm x 1 mm body.