AS1923

Quad-Volta ge Microprocessor Supervisory Circuit

Produ ct Brief

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Revision 1.00

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1 General Description

The AS1923 microprocessor supervisory circuit was

designed to monitor up to four system supply voltages

without the need for external components, and asserts a

single reset if any of the monitored supply voltages

drops below its reset threshold.

The AS1923 features an active-low reset output that is

asserted when any of the 4 monitored voltages are

below their respective reset threshold. The reset output

is open-drain with a weak internal pullup (10µA) to IN2.

Reset remains low for a specified reset timeout period

(120ms min) after all voltages have stabilized. The out-

put is valid as long as the IN1 or IN2 input voltage

remains >1V.

Minimal external component requirements, small size,

and wide temperature range (-40 to +85°C) greatly

improves reliability compared to individual supervisory

circuits or discrete components.

A wide range of factory-trimmed threshold voltages are

available to accommodate many different supply volt-

ages/tolerances with minimal external component

requirements.

Factory-trimmed options are available for monitoring

+5.0, +3.3, +3.0, +2.5, +1.8, and -5.0V supplies with -5%

and/or -10% tolerances. The device is also available

with one or two user-adjustable threshold options (via

external resistor-divider network) if non-standard voltage

thresholds are required.

The AS1923 is available in an 6-pin SOT23 package.

Figure 1. Application Diagram and Pinout

2 Key Features

!

Simultaneous Quad-Voltage Monitoring

!

Precision Factory-Trimmed Reset Threshold

Options: +5.0, +3.3, +3.0, +2.5, +1.8, and -5.0V

!

User-Adjustable Voltage Monitoring Threshold

Options

!

Low Supply Current: 55µA

!

Open-Drain – AS1923A

!

10µA Current Source Pullup – AS1923B

!

Reset Timeout Period: 120ms

!

RESET Valid to IN1 = 1V or IN2 = 1V

!

Immune to Fast INx Transients

!

External Components not Required

!

Guaranteed Performance: Operating Temperature

Range = -40 to +85ºC

!

6-pin SOT23 package

3 Applications

The device is ideal for portable and battery-powered

systems, embedded controllers, intelligent instruments,

automotive systems, critical CPU monitoring, and any

multi-supply application.

4

IN1

GND

2

AS1923

CPU

Monitoring

Voltage 1

Monitoring

Voltage 2

Monitoring

Voltage 3

Monitoring

Voltage 4

6

IN3

1

IN4

5

IN2

3

RESETN

RESETN

AS1923

2

GND

3

RESETN

1

IN4

4 IN1

5 IN2

6 IN3