Alliance Semiconductor ASM1812 Service Manual

查询ASM1812供应商

February 2005

rev 1.4

General Description

The ASM1812 is a voltage supervisory device with low-power,

5V µP Reset, active HIGH, Push-Pull output. Maximum supply

current over temperature is a low 20µA.

The ASM1812 issues an active HIGH reset signal whenever

the monitored supply is out of tolerance. A precision reference

and comparator circuit monitor power supply (V

Tolerance level options are 5%, 10% and 15%. When an out-of-

tolerance condition is detected, an internal power-fail signal is

generated which forces an active HIGH reset signal. After V

returns to an in-tolerance condition, the reset signal remains

active for 150ms to allow the power supply and system

microprocessor to stabilize.

The ASM1812 is designed with a push-pull output stage and

operates over the extended industrial temperature range.

Devices are available in TO-92 and compact surface mount

SOT-23 packages.

Low Power 5V µP Reset Active HIGH, Push-Pull Output

) level.

CC

Applications

• Set-top boxes

• Cellular phones

•PDAs

• Energy management systems

• Embedded control systems

• Printers

• Single board computers

Typical Operating Circuit

CC

V

CC

ASM1812

RESET

ASM1812

Microprocessor

RESET

Other low power products in this family include the ASM1810/

11/15/16/17, ASM1233D and ASM1233M.

Key Features

• Low Supply Current

•20 µA maximum (5.5 V)

• Automatically restarts a microprocessor after power failure

• 150ms reset delay after V

dition

• Active HIGH power-up reset

• Precision temperature-compensated voltage reference and

comparator

• Eliminates external components

• TO-92 and compact surface mount SOT-23 package

• Push-Pull output for minimum current drain

• Operating temperature -40°C to +85°C

returns to an in-tolerance con-

CC

GND

Block Diagram

V

V

2

CC

CC

Supply

Supply

Tolerance

Tolerance

Bias

Bias

Reference

Reference

ASM1812

+

+

-

-

Delay

150ms

Typical

GND

1

RESET

3

Alliance Semiconductor

2575 Augustine Drive . Santa Clara, CA 95054 . Tel: [phone] . Fax: [phone] . www.alsc.com

Notice: The information in this document is subject to change without notice

February 2005

rev 1.4

Pin Configuration

SOT-23

RESET

1

ASM1812

TO-92

ASM1812

V

2

CC

Pin Description

TO-92 SOT-23

Pin # Pin #

1 1 RESET Active HIGH reset output

22

3 3 GND Ground

ASM1812-R

3

GND

2

1

Pin Name Description

V

CC

Power supply input

3

Low Power 5V µP Reset

Notice: The information in this document is subject to change without notice

2 of 9

February 2005

rev 1.4

Application Information

ASM1812

Operation - Power Monitor

The ASM1812 detects out-of-tolerance power supply

conditions. It resets a processor during power-up, power-

down and issues a reset to the system processor when the

monitored power supply voltage is below the reset threshold.

When an out-of-tolerance V

RESET signal is asserted. On power-up, RESET is kept

active (HIGH) for approximately 150ms after the power

supply voltage has reached the selected tolerance. This

allows the power supply and microprocessor to stabilize

before RESET is released.

voltage is detected, the

CC

ASM1812

Microprocessor

RESET

RESET

V

(MIN)

CCTP

~

~

V

CC

~

~

RESET

Figure 2: Timing Diagram: Power-Up

t

R

V

(MAX)

CCTP

V

CCTP

t

RPU

V

OL

Figure 1: Typical Application

V

CC

V

(MAX)

CCTP

RESET

Figure 3: Timing Diagram: Power-Down

Low Power 5V µP Reset

V

CCTP

t

F

V

(MIN)

CCTP

~

~

t

RPD

V

OH

~

~

RESET Slews with V

CC

3 of 9

Notice: The information in this document is subject to change without notice