Dual-voltage supervisor in a 4-pin SC-70
The MAX6389XS29D3+T is a multi-voltage supervisor from Analog Devices that monitors two supply rails — one fixed at 2.93V and a second adjustable via external resistors — and asserts an active-low, open-drain reset output when either falls below its threshold. The reset remains asserted for a minimum of 140ms after both rails recover, giving the system time to stabilize before the processor starts executing code.
Threshold selection and reset timing
The fixed threshold of 2.93V is intended for a 3.0V or 3.3V rail with typical tolerance — the supervisor trips before the rail drops below the processor's minimum operating voltage. The second channel's adjustable input lets the designer set a trip point for a lower-voltage core or I/O supply using a resistor divider. Both channels share a single open-drain output, so the reset signal is the wired-OR of the two undervoltage events. The 140ms minimum reset timeout is long enough to cover most power-supply ramp-up and hold-up capacitor discharge profiles, but short enough that the system does not linger in reset during a brief brownout.
Sourcing and compliance posture
It is available in tape-and-reel or cut-tape formats in the SC-82A/SOT-343 package that maps to a SC-70-4 footprint.