Battery backup supervisor for 5V rails
The MAX690AESA+T from Analog Devices is a battery backup supervisor IC that monitors a single 5V supply rail. It asserts a reset output when the supply drops below the 4.65V threshold and holds it low for a minimum of 140ms after the rail recovers, giving the system time to stabilize. The push-pull, totem-pole output is active low, which is the standard polarity for most MCU reset inputs. This is the tape-and-reel variant (the +T suffix), so it arrives on a reel ready for pick-and-place — the cut-tape version is also available if you are prototyping.
What the 4.65V threshold means for your rail
The 4.65V threshold is set for a nominal 5V supply. That is about 7% below 5V, so it catches a brownout before the logic rails droop enough to cause erratic behaviour. If your system runs on 3.3V or 2.5V, this is not the part — you want a supervisor with a threshold closer to those levels. The 140ms minimum reset timeout is generous enough to cover most power-supply ramp times and oscillator start-up delays without needing an external capacitor to stretch the pulse.
Industrial temperature grade, active lifecycle
Rated for -40°C to 85°C, this supervisor handles industrial environments — factory-floor controllers, outdoor telecom gear, anything that sees a cold morning or a warm cabinet. The part is listed as active, so there is no last-time-buy pressure for current designs. It is also ROHS3 compliant, which clears it for lead-free assembly lines without an exemption review.
Package and mounting
Housed in an 8-SOIC package (0.154" body width, 3.90mm wide), it is a standard surface-mount footprint that fits on any PCB without special routing. The supplier device package is also 8-SOIC, so the marking matches the land pattern. No thermal pad to worry about — this is a low-power supervisor, so dissipation is not a concern.