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AS1923

Datasheet - Detailed Descr i pti on

8 Detailed Description

The AS1923 is a very small, low-power, quad-voltage microprocessor supervisory circuit designed to maintain system integrity in multi-supply

systems (see Figure 10). The device offers several factory-trimmed under-voltage threshold values that minimize or eliminate the need for exter-

nal components.

Preset voltage monitoring values of +5.0, +3.3, +3.0, +2.5, +1.8, and -5.0V (see Ordering Information on page 14) are available for a wide range

of applications such as telecommunications equipment, desktop and notebook computers, high-end printers, data storage equipment, and net-

working equipment applications.

also designed to ignore fast INx transients.

Figure 10. AS1923 - Block Diagram

The quad-voltage monitor/reset circuitry includes an accurate bandgap reference, four precision comparators, and a series of internal trimmed

resistor-divider networks to set the factory-trimmed reset threshold values.

The resistor networks scale the specified INx reset voltages to match the internal bandgap reference/comparator voltage. User-adjustable

threshold options bypass the internal resistor networks and connect directly to one of the comparator inputs (an external resistor-divider network

is required for threshold matching).

Each of the internal comparators has a typical hysteresis of 0.5% with respect to its reset threshold. This built-in hysteresis improves device

immunity to ambient noise without significantly reducing threshold accuracy when an input sits at its specified reset voltage.

Note:

Threshold voltage options (fixed and adjustable) are designated by the single-letter code in the model number (see Ordering Informa-

tion on page 14).

AS1923

+

–

+

–

+

–

+

–

4

IN1

6

IN3

1

IN4

5

IN2

Timeout

(220ms)

5V Pullup

3

RESETN

3V

Bandgap

Reference

IN1

Optional on AS1923B Only