MAX690S(1994) 查看數據表（PDF） - Maxim Integrated

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MAX690S
(Rev.:1994)

3.0V/3.3V Microprocessor Supervisory Circuits

Maxim Integrated 

3.0V/3.3V Microprocessor Supervisory Circuits

______________________________________________________________Pin Description

PIN

MAX690 MAX704 MAX804 NAME

MAX802 MAX806 MAX805

FUNCTION

Supply Output for CMOS RAM. When VCC is above the reset threshold, VOUT is

1

1

1

VOUT connected to VCC through a P-channel MOSFET switch. When VCC falls below VSW and

VBATT, VBATT connects to VOUT. Connect to VCC if no battery is used.

2

2

2

VCC Main Supply Input

3

3

3

GND Ground

4

4

4

PFI

Plooww; eort-hFeariwl Iinspe,u–Pt—. F—WO–hreenmPaFinI sishliegshs.

than VPFT or when VCC falls below

Connect to ground if unused.

VSW,

–P—F—O–

goes

5

5

5

–P—F—O–

Power-Fail

otherwise,

–PO—F—uOtp–uret.mWaihnesnhPigFhI.isLeleasvsetohpanenVPifFuTn, uosreVdC.C

falls

below

VSW,

–P—F—O–

goes

low;

Watchdog Input. If WDI remains high or low for 1.6sec, the internal watchdog timer runs out

6

—

6

WDI and reset is triggered. The internal watchdog timer clears while reset is asserted or when

WDI sees a rising or falling edge. The watchdog function cannot be disabled.

—

6

—

–M—R–

–MM—aR–niusalloRweasnedt Ifnopru2t0. 0Amlosgaicftelorw–M—oR–nr–Me—tRu–rnasssheigrths.reTsheist.

Reset remains

active-low input

asserted as long

has an internal

as

70µA pull-up current. It can be driven from a TTL or CMOS logic line, or shorted to

ground with a switch. Leave open if unused.

7

7

—

–R—E—S—E—T– AVeiCcthtCievires-VLbCoeCwlorwRiseethsseeatrbOeosuvetept tuthhtr.eePsrehusolseldet stohlrroewwshhfeoonrld2–M,—0tR0h–meisswaawtlhoceghndicotrlgoigwtgr.iegIrtgereder,msaaanindressslteoatwy, soforlor–Mw—2R0–w0ghmoesenseavfteerr

from low to high.

—

—

7

RESET Active-High, Open-Drain Reset Output is the inverse of –R—E—S—E—T–.

Backup-Battery Input. When VCC falls below VSW and VBATT, VOUT switches from VCC to

8

8

8

VBATT VBATT. When VCC rises above the reset threshold, VOUT reconnects to VCC. VBATT may

exceed VCC. Connect to VCC if no battery is used.

_______________Detailed Description

Reset Output

A microprocessor’s (µP’s) reset input starts the µP in a

known state. These µP supervisory circuits assert reset to

prevent code execution errors during power-up, power-

down, brownout conditions, or a watchdog timeout.

–R—E—S—E—T– is guaranteed to be a logic low for 0V < VCC <

VaRbSaT,ckpuropvibdaetdtertyh,at–R—VE—BS—AE—TTT–

is

is

greater than 1V.

guaranteed valid

Without

for VCC

> 1V.

internal

period;

aOtfimtnecer erthkiVseCeinCpteservx–R—acEl—e,Se—–R—Ed—E—sT–S—tlE—ohTw–e grfooeersseththeitghrheres(Fseihtgoutilmrdee,2oa)u.nt

Irfesaetbtrhorwesnhooultd)c,o–Rn—dE—iSt—ioE—nT– ogcoceusrslow(V. CECacdhiptsimbee–Rl—oE—wS—tE—hTe–

is asserted, it stays low for the reset timeout period.

Any time VCC goes below the reset threshold, the

internal timer restarts.

The watchdog timer can also initiate a reset. See the

Watchdog Input section.

The MAX804_/MAX805_ active-high RESET output is

open drain, and the

MAX802_/MAX806_

–Ri—nE—veS—rEs—eT–

of the MAX690_/MAX704_/

output.

Reset Threshold

The MAX690T/MAX704T/MAX805T are intended for

3.3V systems with a ±5% power-supply tolerance and a

10% system tolerance. Except for watchdog faults,

reset will not assert as long as the power supply

remains above 3.15V (3.3V - 5%). Reset is guaranteed

to assert before the power supply falls below 3.0V.

The MAX690S/MAX704S/MAX805S are designed for

3.3V ±10% power supplies. Except for watchdog

faults, they are guaranteed not to assert reset as long

as the supply remains above 3.0V (3.3V - 10%). Reset

is guaranteed to assert before the power supply falls

below 2.85V (VCC - 14%).

The MAX690R/MAX704R/MAX805R are optimized for

monitoring 3.0V ±10% power supplies. Reset will not

occur until VCC falls below 2.7V (3.0V - 10%), but is

guaranteed to occur before the supply falls below

2.59V (3.0V - 14%).

The MAX802R/S/T, MAX804R/S/T, and MAX806R/S/T

are respectively similar to the MAX690R/S/T,

MAX805R/S/T, and MAX704R/S/T, but with tightened

reset and power-fail threshold tolerances.

6 _______________________________________________________________________________________

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