DS1231-20

The DS1231-20 from Dallas Semiconductor is a power monitor chip that enhances system reliability by monitoring input power and a 5V system power supply. It utilizes precise, temperature-compensated comparators to detect unsafe voltage levels. Upon detection of an unsafe condition, it sends a non-maskable interrupt to the processor, providing a warning signal in advance of power failure. Processing is halted when power falls below a user-selectable 5% or 10% threshold.

This power monitor chip offers an operating temperature range of 0°C to +70°C for the DS1231 and DS1231S variants, and -40°C to +85°C for the DS1231-N and DS1231S-N variants. Key specifications include a reset threshold range of 3.3V to 5.5V, a reset timeout range of 85ms to 300ms, and a maximum ICC of 2000µA. The reset threshold accuracy is 2.5% at +25°C. It features an open-drain active-low reset output and supports optional active-low NMI hysteresis with values of 200mV, 350mV, or 500mV.

The DS1231-20 automatically restarts the processor on power-up and pauses the restart until system conditions stabilize. It also initiates and holds the processor reset until unsafe levels are detected. All external reset components, such as pull-up resistors and delay timing capacitors, are contained within the package, saving space and cost. An input sense supports connection to switched inputs like an opto-isolator for LED functions.