©

1999 IMP, Inc.

408-432-9100/www.impweb.com

1

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)

Block Diagram

RESET

PBRST

1 (2)

1232_03.eps

40k

Ω

TOL

IMP1232LP/LPS

(16-Pin Package)

3 (6)

–

+

5%/10% Tolerance

Selection

Reference

8 (15)

RESET

5 (9)

TD

Push Button

Debounce

2 (4)

Watchdog

Timebase Selection

GND

4 (8)

Reset &

Watchdog Timer

6 (11)

ST

7 (13)

Watchdog

Transition Detector

IMP1

232LP/LPS

5V

or and

R

cuit

– Select

ance

and W

iod

– Push-Butt

eset

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

power supply falls outside selectable tolerance limits, both the RESET

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.

A debounced manual reset input activates the reset outputs for a mini-

mum period of 250ms.

Also included is a watchdog timer to stop and restart a microprocessor

that is “hung-up”. Three watchdog time-out periods are selectable:

150ms, 610ms and 1,200ms. If the ST input is not strobed

LOW before the time-out period expires, a reset is issued.

Devices are available in 8-pin DIP, 8/16-pin SO and com-

pact 8-pin MicroSO packages.