IMP1 232LP/LPS
P
OWER
M
ANAGEMENT
5V µP Power Supply Monitor and
Reset Circuit
– Selectable Trip -Point Tolerance
and Watchdog Period
– Push-Button Reset
Key Features
x
Pin compatible with the Dallas Semiconductor
DS1232LP/1232LPS
— 40% lower supply current
x
5V supply monitor
x
Selectable watchdog period
x
Debounce manual push-button reset input
x
Precision temperature-compensated voltage
reference and comparator
x
Power-up, power-down and brownout detection
x
250ms reset time
x
Active LOW open-drain reset and active HIGH
push-pull output
x
Selectable trip point tolerance: 5% or 10%
x
Low-cost, surface mount packages: 8/16-pin
SO, 8-pin DIP and 8-pin MicroSO
x
Wide operating temperature – 40°C to +85°C
(N/EPA suffixed devices)
The IMP1232LP/LPS microprocessor supervisor can halt and restart a
“hung-up” or “stalled” microprocessor, restart a microprocessor after a
power failure, and debounce and interface a manual push-button micro-
processor reset switch. The low-power supervisors feature 40% lower
supply current than the pin compatible Dallas Semiconductor
DS1232LP/LPS.
Precision temperature compensated reference and comparator circuits
monitor the 5V, V
CC
input voltage. During power-up or when the V
CC
power supply falls outside selectable tolerance limits, both the 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-percent.
Each device has both a push-pull, active HIGH reset output and an open
drain, active LOW reset output.
150ms, 610ms and 1,200ms. If the ST input is not strobed
A debounced manual reset input activates the reset outputs for a mini- LOW before the time-out period expires, a reset is issued.
mum period of 250ms.
Devices are available in 8-pin DIP, 8/16-pin SO and com-
Also included is a watchdog timer to stop and restart a microprocessor pact 8-pin MicroSO packages.
that is “hung-up”. Three watchdog time-out periods are selectable:
Block Diagram
V
CC
TOL
8 (15)
IMP1232LP/LPS
3 (6)
5%/10% Tolerance
Selection
(16-Pin Package)
6 (11)
RESET
+
5 (9)
V
CC
Reference
–
RESET
40kΩ
PBRST
1 (2)
Push Button
Debounce
Watchdog
Timebase Selection
Watchdog
Transition Detector
4 (8)
1232_03.eps
TD
2 (4)
Reset &
Watchdog Timer
ST
7 (13)
GND
©
1999 IMP, Inc.
408-432-9100/www.impweb.com
1
IMP [ IMP, INC ]
