MAX690 Просмотр технического описания (PDF) - Maxim Integrated

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MAX690

Microprocessor Supervisory Circuits

Maxim Integrated 

MAX690–MAX695

Microprocessor Supervisory Circuits

General Description

The MAX690 family of supervisory circuits reduces the

complexity and number of components required for

power supply monitoring and battery control functions in

microprocessor systems. These include µP reset and

backup-battery switchover, watchdog timer, CMOS RAM

write protection, and power-failure warning. The MAX690

family significantly improves system reliability and accu-

racy compared to that obtainable with separate ICs or

discrete components.

The MAX690, MAX692, and MAX694 are supplied in

8-pin packages and provide four functions:

●● A reset output during power-up, power-down, and

brownout conditions.

●● Battery backup switching for CMOS RAM, CMOS

microprocessor or other low power logic.

●● A Reset pulse if the optional watchdog timer has not

been toggled within a specified time.

●● A 1.3V threshold detector for power fail warning, low

battery detection, or to monitor a power supply other

than +5V.

The MAX691, MAX693, and MAX695 are supplied in 16-pin

packages and perform all MAX690, MAX692, MAX694

functions, plus:

●● Write protection of CMOS RAM or EEPROM.

●● Adjustable reset and watchdog timeout periods.

●● Separate outputs for indicating a watchdog timeout,

backup-battery switchover, and low VCC.

Typical Operating Circuit

+5V

VCC

VOUT

POWER TO

µP

VBATT

CMOS RAM POWER

MAX690

µP

SYSTEM

PFI

RESET

PFO

WDI

GND

µP RESET

µP NMI

I/O

LINE

MAX690 TYPICAL APPLICATION

Benefits and Features

●● Supervisory Function Integration Saves Board Space

while Fully Protecting Microprocessor-Based Systems

• Precision Voltage Monitor

-- 4.65V (MAX690, MAX691, MAX694, MAX695)

-- 4.40V (MAX692, MAX693)

• Power OK/Reset Time Delay

-- 50ms, 200ms, or Adjustable

• Watchdog Timer

-- 100ms, 1.6s, or Adjustable

• Battery Backup Power Switching

• Voltage Monitor for Power Fail or Low Battery

Warning

• Minimum External Component Count

●● Low Power Consumption in Battery Backup Mode

Extends Battery Life

• 1µA Standby Current

●● Onboard Gating of Chip Enable Signals Protects

Against Erroneous Data Written to RAM During Low

VCC Events

Applications

●● Computers

●● Controllers

●● Intelligent Instruments

●● Automotive Systems

●● Critical µP Power Monitoring

Ordering information appears at end of data sheet.

Pin Configurations

TOP VIEW

VOUT 1

VCC 2

GND 3

PFI 4

MAX690

MAX692

MAX694

8 VBATT

7 RESET

6 WDI

5 PFO

VBATT 1

VOUT 2

VCC 3

GND 4

BATT ON 5

LOW LINE 6

OSC IN 7

OSC SEL 8

MAX691

MAX693

MAX695

16 RESET

15 RESET

14 WDO

13 CE IN

12 CE OUT

11 WDI

10 PFO

9 PFI

19-0218; Rev 5; 4/15

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