DS1831/A/B

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OPERATION—POWER MONITOR

The DS1831 provides the functions of detecting out-of-tolerance conditions on a 3.3V (or 3V) and 5V

power supply and warning a processor-based system of impending power failure. When an input is

with the associated TD input and then return to an inactive state until the next input out-of-tolerance

condition.

On power-up both resets are kept active for the selected reset time after the associated power supply input

has reached the selected tolerance. This allows the power supply and system power to stabilize before

RST

is released.

ever has the highest voltage level.

OPERATION—TOLERANCE SELECT

The DS1831 provides two TOL inputs for individual customization of the DS1831 to specific application

requirements. If the TOL for the 5V supply is tied to the 5V input a 5% tolerance is selected. If the TOL

is connected to ground a 10% tolerance is selected or if it is left unconnected a 15% tolerance is selected.

If the TOL for the 3.3V supply is tied to the 3.3V input a 5% tolerance is selected, a 10% tolerance is

selected if it is connected to ground, and a 20% tolerance is selected if the input is left unconnected.

These tolerance conditions are set at power up and can only be changed by power cycling the device.

OPERATION—RESET TIME-DELAY SELECT

The DS1831 provides two TD inputs for individual customization of reset time-delays and an additional

the Watchdog on the DS1831A. The reset time delays are shown in Table 1. These allow the selection of

minimum delays of 10ms, 100ms, and 1000ms.

Wiring an individual reset output to the push-button input of the other voltage reset allows custom reset

timings or allows for the sequencing of the reset outputs. See Figure 2.

These time-delays are set at power-up and cannot be changed after the device reaches an in-tolerance

condition.

TD INPUTS/RESET AND WATCHDOG TIME-DELAYS Table 1

RESET TIME-DELAY

TD

MIN

TYP

MAX

GND

10ms

16ms

20ms

Float

100ms

160ms

200ms

1000ms

1600ms

2000ms