Key Features

Applications

x

Embedded control systems

x

Battery–operated systems

x

Intelligent instruments

x

Wireless communication systems

x

PDAs and handheld equipment

x

µP/µC power supply monitoring

x

Design improvement over Maxim

MAX690A/692A/802L/802M/805L

— 70% lower current than Maxim:

100

µA maximum

— RESET Operation to 1.1V

x

Two precision supply-voltage monitor options

— 4.65V (IMP690A/802L/805L)

— 4.40V (IMP692A/802M)

x

Battery-backup power switch on-chip

x

Watchdog timer: 1.6 second timeout

x

Power failure/low battery detection

x

Short-circuit protection and thermal limiting

x

Small 8-pin SO package

x

No external components

x

Specified over full temperature range

Block Diagrams

+

–

GND

Unregulated DC

Regulated +5V

WDI

3.6V

Lithium

Battery

0.1

µF

PFO

PFI

RESET

RESET

GND

GND

CMOS

RAM

NMI

I/O LINE

690A_01.eps

IMP690A

IMP690A

, 802L/M, 805L

µ

visor

wit

The IMP690A/IMP692A/IMP802L/IMP802M/IMP805L simplify power

supply monitoring and control in microprocessor systems. Each circuit

implements four functions: Reset control, watchdog monitoring, battery-

backup switching and power-failure monitoring. In addition to

microprocessor reset under powerup and power-down conditions, these

devices provide battery-backup switching to maintain control in power-

loss and brown-out situations. Additional monitoring capabilities

can provide an early warning of unregulated power-supply loss before

the voltage regulator drops out. The important features of these four

functions are:

a)

1.6 second watchdog timer to keep microprocessor responsive

b)

and power-down

c)

SPDT (single-pole, double-throw) PMOS switch connects backup

d) 1.25V threshold detector for power loss or general purpose voltage

monitoring

While these features are pin–compatible with the industry standard

power–supply supervisors offered by Maxim, the IMP devices are supe-

rior replacements and can reduce power requirements by 70 percent

when compared to Maxim MAX690/MAX692A/MAX802L/MAX802M/

MAX805L devices. Short-circuit and thermal protection have also

been added.

The IMP690A/IMP802L/IMP805L generate a reset pulse when the

supply voltage drops below 4.65V, and the IMP692A/IMP802M

generate a reset below 4.40V. The IMP802L/IMP802M have power–fail

accuracy to ±2%. The IMP805L is the same as the IMP690A except that

RESET is provided instead of



RESET.

IMP, Inc.

San Jose, CA

408-432-9100/www.impweb.com

+

+

+

1

7

5

3

PFI

WDI

GND

8

2

6

4

PFO

IMP690A, IMP692A, IMP802L, IMP802M,

IMP805L

RESET

(RESET)

( ) IMP805L

Battery-Switchover

Circuit

Reset

Generator

Watchdog

Timer

3.5V

1.25V

1.25V

0.8V

690A_03.eps

Typical Application