The MIC1232 is a multifunction circuit which monitors microprocessor activity, external reset and power supplies in microprocessor based systems. The circuit functions include a watchdog timer, power supply monitor, microprocessor reset, and manual pushbutton reset input. The power supply line is monitored with a comparator and an internal voltage reference. RST is forced low when an out-of-tolerance condition exists and remains asserted for at least 250ms after VCC rises above the threshold voltage (4.5V or 4.75V). The RST pin will remain logic low with VCC as low as 1.4V. The Watchdog input (ST) monitors µP activity and will assert RST if no µP activity has occurred within the watchdog timeout period. The watchdog timeout period is selectable with nominal periods of 150, 600, or 1200 milliseconds.
The MIC1232 is a multifunction circuit designed to monitor microprocessor activity, external resets, and power supplies. It integrates functions such as a selectable watchdog timer, a precision power supply monitor with 5% or 10% tolerance options, and a debounced manual pushbutton reset input.
The device ensures system stability by asserting the RST output low when voltage drops below a threshold, the watchdog times out, or an external reset is triggered. It remains asserted for at least 250ms after power stabilizes to ensure proper microprocessor initialization.
| Supply Voltage Range | 4.5V to 5.5V |
|---|---|
| Watchdog Timeout Period (TD=Open) | 250ms to 1000ms typical |
| Supply Current | < 40 pA typical |
| Reset Active Time | 250ms to 1000ms typical |
| Operating Temperature Range (MIC1232N/M) | -40°C to +85°C |
| Output Source Current (RST) | 10 mA typical |
The watchdog timeout period is selectable with nominal periods of 150ms, 600ms, or 1200ms depending on the TD pin state.
The tolerance is selected by connecting the TOL pin to ground for a 5% level or to VCC for a 10% level.
Any pulse with a duration of 20ms or greater on the PBRST pin is guaranteed to cause a reset.