Monitoring power supplies in computers and digital systems

Louise Smyth

Diodes has developed a micro-power voltage detector to help monitor the power lines in embedded computer systems.

The APX803L is designed to support the supervisory circuits of microprocessors and microcontrollers, generating a reset signal whenever a supply rail falls below a defined threshold.

This function is required by many systems, including computers and communications equipment, but particularly portable battery-powered devices.

A key aspect of the sensor is the low quiescent current that makes it very attractive when the system is in standby mode.

With a detection voltage level range of 1.2V to 5.0V in 0.1V steps, the APX803L provides a threshold accuracy of ±1.5%, while consuming just 1μA and requiring no external components.

Whenever the supply rail drops below the chosen threshold, the APX803L triggers a reset signal within 20μs that is held until the supply rail recovers to a level above the threshold.

The reset pin provides an open-drain, active-low output with device ordering options that allow for delay times of 0ms, 55ms, 220ms, or 450ms.

The sensor is available in 3-pin SOT23, SOT323, and SC59 packages and a 5-pin SOT25 package for drop-in replacement and original designs.