MAX690R 查看數據表（PDF） - Maxim Integrated

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MAX690R

3.0V/3.3V Microprocessor Supervisory Circuits

Maxim Integrated 

3.0V/3.3V Microprocessor Supervisory Circuits

VBATT

VCC

BATTERY

SWITCHOVER

VOUT

CIRCUITRY

BATTERY

SWITCHOVER

COMPARATOR

1.237V

RESET

COMPARATOR

1.237V

MAX690T/S/R

MAX704T/S/R

MAX802T/S/R

MAX804T/S/R

MAX805T/S/R

MAX806T/S/R

3.0V OR 3.3V

VCC

0V

3.0V OR 3.3V

VOUT

VSW

3.0V OR 3.3V

RESET

VBATT = 3.6V

VRST

VSW

tWP

WDI *

**

MR

PFI

*

WATCHDOG

TIMER

RESET

GENERATOR

POWER-FAIL

COMPARATOR

VPFT

RESET

(RESET)

PFO

* MAX690T/S/R, MAX802T/S/R, MAX804T/S/R, MAX805T/S/R ONLY

** MAX704T/S/R, MAX806T/S/R ONLY

( ) MAX804T/S/R, MAX805T/S/R ONLY

Figure 1. Block Diagram

(RESET)

PFO

VBATT = PFI = 3.6V

IOUT = 0mA

( ) MAX804T/S/R, MAX805T/S/R ONLY, RESET EXTERNALLY PULLED UP TO VCC

Figure 2. Timing Diagram

Watchdog Input

(MAX690_/802_/804_/805_)

The watchdog circuit monitors the µP’s activity. If the µP

does not toggle the watchdog input (WDI) within 1.6sec,

a reset pulse is triggered. The internal 1.6sec timer is

cleared by either a reset pulse or by a transition (low-to-

h–R—igE—hS—Eo—rT–hpiguhls-teo-islotwrig) gaterWedDIe. vIefrWy 1D.I8sisectie(dtWhDigphluosrtRloSw)., a

As long as reset is asserted, the timer remains cleared

and does not count. As soon as reset is deasserted,

the timer starts counting. Unlike the 5V MAX690 family,

the watchdog function cannot be disabled.

Power-Fail Comparator

The

PFI

PFI input is

is less than

cVoPmFTp, a–Pr—eF—dO–togaonesinltoewrn.aTl hreefeproewnceer-.faIifl

comparator is intended for use as an undervoltage

detector to signal a failing power supply. However, the

comparator does not need to be dedicated to this

function because it is completely separate from the rest

of the circuitry.

The power-fail comparator turns off and –P—F—O– goes low

when VCC falls below VSW on power-down. The power-

fail comparator turns on as VCC crosses VSW on

cpgooronwunenerdc-utepad.nIdftotlhe–Mea—Rvc–eoom–nP—pF—tahOre–atMournAcisXo7nn0on4te_uc/sMteeAddX., 8c–P—0oF6—n_On–escomt atPhyFaItbtaeo

low voltage on PFI will generate a reset (Figure 5b).

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