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
asserted and remains asserted for atleast 800ms after V
CC
has
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
temperature ranges 0
0
to 70
0
c and -40
0
c to +85
0
c.
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
• Two temperature ranges: 0
0
to 70
0
c and -40
0
c to +85
0
c
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
M48
J4.0
T38
S2.93
R26
V
CC
MR
(RESET)
GND
(RESET)
µP
ASM161
(ASM162)
RESET RESET
V
CC
GND
V
CC
20k for
ASM161
only