ASM161 / ASM162

Alliance Semiconductor

2575 Augustine Drive . Santa Clara, CA 95054 . Tel: 408.855.4900 . Fax: 408.855.4999 . www.alsc.com

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

rev 1.0

µP Supervisory Circuit

October 2003

General Description

The ASM161 and ASM162 are cost effective, low power

supervisory

circuits

that

monitor

power

supplies

in

microprocessor, microcontroller and digital systems. If the

power supply drops below the reset threshold level, a reset is

risen above the reset threshold. An improved manual reset

architecture gives the system designer additional flexibility.

The debounced manual reset input is negative edge triggered.

The reset pulse period generated by a MR transition is a

minimum of 800 ms and a maximum of 2 sec duration. In

addition, The MR input signal is blocked for an additional 49µS

minimum after the reset pulse ends. During the MR disable

period, the microcontroller is guaranteed a time period free of

additional manual reset signals. During this period DRAM

contents can be refreshed or other critical system tasks

undertaken. Low power consumption makes the ASM161/162

ideal for use in portable and battery operated equipments. With

3V supplies power consumption is 8µW typically and 30µW

maximum. The ASM161 has an open-drain, active-LOW

RESET output and requires an external pull-up resistor. The

ASM162 has an active HIGH RESET output.

The ASM161/162 are offered in compact 4-pin SOT-143

packages. No external components are required to trim

threshold voltage for monitoring different supply voltages. With

six different factory set, reset, threshold ranges from 2.63V to

4.63V, the ASM161/162 are suitable for monitoring 5V, 3.6V

and 3.0V supplies. The ASM161/162 are available in

Key Features

•

Edge triggered manual reset input

•

single pulse output

•

49µS minimum MR disable period after reset

•

CMOS/TTL logic or switch interface

•

Debounced input

•

Low supply current extends battery life

• 6µA / 15µA typ/max at 5.5V

• 4.5µA / 10µA typ/max at 3.6V

•

Long reset period

• 0.8 sec minimum, 2 sec maximum

•

Two reset polarity options

• ASM161: Active LOW, open-drain

• ASM162: Active HIGH

•

Pinout matches the AS811/812

•

Small 4-Pin SOT-143 package

•

Applications

•PDAs

•

Appliances

•

Computers and embedded controllers

•

Wireless communication systems

•

Battery operated and intelligent instruments

•

Automotive systems

•

Safety systems

Typical Operating Circuit

Reset Threshold

Part Suffix

Voltage (V)

L4.63

M4.38

J4.00

T3.08

S2.93

R2.63

MR

(RESET)

GND

(RESET)

µP

ASM161

(ASM162)

RESET

RESET

GND

20k for

ASM161

only