Dual-voltage supervisor with adjustable threshold — what it does on the board
The TPS3421ECDRYR is a two-channel voltage supervisor that monitors up to two supply rails and asserts a common active-low reset output when either rail falls below its adjustable threshold. The open-drain output requires a pull-up resistor to the monitored or system logic rail — factor that into the BOM. Reset timeout is a minimum of 64 ms, long enough to let both supplies settle after power-up before the processor is released from reset. Surface-mount assembly is standard.
64 ms reset timeout — what it means for power-up sequencing
The 64 ms minimum reset timeout is the window the supervisor holds the reset line low after all monitored voltages are above threshold.
Open-drain output — pull-up selection and bus sharing
The open-drain output lets multiple supervisors share a common reset bus — wire-AND them together so any fault pulls the line low.