ASM1232LP Datasheet, PDF (1/10 Pages) Alliance Semiconductor Corporation – 5V uP Power Supply Monitor and Reset Circuit

November 2006
ASM1232LP/LPS
rev 1.6
5V µP Power Supply Monitor and Reset Circuit
General Description
The ASM1232LP/LPS is a fully integrated microprocessor
supervisor. It can halt and restart a “hung-up” microprocessor,
restart a microprocessor after a power failure. It has a
watchdog timer and external reset override.
• Low-cost surface mount packages: 8-pin/16-pin SO, 8-pin
DIP and 8-pin Micro SO packages
• Wide operating temperature -40°C to +85°C (N suffixed
devices)
Applications
A precision temperature-compensated reference and
comparator circuits monitor the 5V, V_CC input voltage status.
During power-up or when the V_CC power supply falls outside
selectable tolerance limits, both RESET and RESET become
active. When V_CC rises above the threshold voltage, the reset
signals remain active for an additional 250ms minimum,
allowing the power supply and system microprocessor to
stabilize. The trip point tolerance signal, TOL, selects the trip
level tolerance to be either 5% or 10%.
• Microprocessor Systems
• Computers
• Controllers
• Portable Equipment
• Intelligent Instuments
• Automotive Systems
Typical Operating Circuit
Each device has both a push-pull, active HIGH reset output and
an open drain active LOW reset output. A debounced manual
reset input, PBRST, activates the reset outputs for a minimum
period of 250ms.
There is a watchdog timer to stop and restart a microprocessor
that is “hung-up”. The watchdog timeouts periods are
selectable: 150ms, 610ms and 1200ms. If the ST input is not
strobed LOW before the time-out period expires, a reset is
generated.
ASM1232LP/LPS
ST
RESET
GND TD TOL
+5V
10kΩ
µP
I/O
RESET
Devices are available in 8-pin DIP, 16-pin SO and compact 8-
pin MicroSO packages.
Block Diagram
Key Features
V_CC
TOL
• 5V supply monitor
• Selectable watchdog period
• Debounce manual push-button reset input
• Precision temperature-compensated voltage reference and
comparator.
PBRST
• Power-up, power-down and brown out detection
TD
• 250ms minimum reset time
• Active LOW open drain reset output and active HIGH
ST
push-pull output
• Selectable trip point tolerance: 5% or 10%
Tolerance Selection
Reference
V_CC
40kΩ
Push Button
Debounce
Voltage Sense
Comparators
Watchdog Transition
Detector
ASM1232LP/LPS
+
-
Reset &
Watchdog Timer
GND
PulseCore Semiconductor Corporation
1715 S. Bascom Ave Suite 200, Campbell, CA 95008 • Tel: [phone] • Fax: [phone]
www.pulsecoresemi.com
Notice: The information in this document is subject to change without notice
RESET
RESET