MAX690T 查看數據表（PDF） - Maxim Integrated
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MAX690T Datasheet PDF : 12 Pages
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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–tP—. 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.isLeleasvsetohpanenViPfFuTn, uosreVdC.C
falls
below
VSW,
–P—F—O–
goes
low;
Watchdog Input. If WDI remains high or low for 1.6s, 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 asserted as long
active-low input has an internal
as
70µA pullup 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– AVeiCcthtCieviresV-LbCoeCwlorwRiseethsseeatrbOeosuvetept 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 <
aVRbSaT,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
reset threshold, an
for the reset timeout
goes high (Figure 2).
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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