ASM1832 Datasheet, PDF (1/9 Pages) Alliance Semiconductor Corporation – 3.3V UP Power Supply Monitor and Reset Circuit

October 2006
ASM1832
rev 1.6
3.3V µP Power Supply Monitor and Reset Circuit
General Description
The ASM1832 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. RESET and RESET outputs are
push-pull.
A precision temperature-compensated reference and
comparator circuits monitor the 3.3V, 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 10% or 20%.
Devices are available in 8-pin PDIP, 8-pin SO and compact 8-
pin MicroSO packages.
Key Features
• 3.3V supply monitor
• Push-pull output
• Selectable watchdog period
• Debounce manual push-button reset input
• Precision temperature-compensated voltage reference
and comparator.
• Power-up, power-down and brown out detection
• 250ms minimum reset time
• Active LOW and HIGH reset signal
• Selectable trip point tolerance: 10% or 20%
• Low-cost 8-pin DIP/SO and 8-pin Micro SO packages
• Wide operating temperature -40°C to +85°C
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.
Applications
• Microprocessor systems
• Computers
• Controllers
• Portable instruments
• Automotive systems
Typical Operating Circuit
Block Diagram
3.3V
ASM1832
ST
RESET
GND TD TOL
µP
I/O
RESET
V_CC
TOL
PBRST
TD
ST
ASM1832
Tolerance Selection
+
-
V_CC
Reference
40KΩ
Push Button
Debounce
Voltage Sense
Comparator
Watchdog
Transition Detector
Reset &
Watchdog Timer
V_CC
RESET
V_CC
RESET
GND
PulseCore Semiconductor Corporation
1715 S, Boscom Ave Suit 200,Campbell, CA 95008. Tel:[phone]. Fax:[phone].
www.pulsecoresemi.com
Notice: The information in this document is subject to change without notice