This application note describes the problems with monitoring the power supply during power-up/reset in a microprocessor system. It also explains how the ST family of Reset Circuits can be used to solve them.
The document addresses the importance of correct power supply voltage for microprocessor functionality, highlighting issues like glitches and slow ramp-ups that can cause system crashes. It discusses limitations of standard Resistor-Capacitor (RC) filter circuits for managing reset delays during power-up and monitoring voltage during operations.
As a solution, the note introduces ST's family of low-power supervisory devices known as Reset Circuits (specifically models STM809 through STM812). These integrated circuits provide precise voltage thresholds and reset delays to ensure system stability. The document details their features, including manual reset inputs for debugging or waking from sleep modes.
| Device Family | STM809, STM810, STM811, STM812 |
|---|---|
| Package Types | SOT23, SOT143 |
| Supply Current | 5-10 µA |
Yes, these devices include a push-button reset input signal (MR) with an internal debounce circuit.
The device asserts a reset signal whenever the power supply drops below a preset threshold value.
The reset signal remains asserted until the voltage rises above that threshold for a minimum period of time.
These devices require only a low supply current, typically in the 5-10 µA range.