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參數(shù)資料
| 型號： | MAX691A |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Microprocessor Supervisory Circuits(帶看門狗復(fù)位、片選和支持備用電池的復(fù)位器) |
| 中文描述： | 微處理器監(jiān)控電路 |
| 文件頁數(shù)： | 8/16頁 |
| 文件大小： | 164K |
| 代理商： | MAX691A |
M
RESET and –————are asserted when V
CC
falls below
the reset threshold (4.65V for the MAX691A/MAX800L,
4.4V for the MAX693A/MAX800M) and remain asserted
for 200ms typ after V
CC
rises above the reset threshold
on power-up (Figure 5). The devices’ battery-
switchover comparator does not affect reset assertion.
However, both reset outputs are asserted in battery-
backup mode since V
CC
must be below the reset
threshold to enter this mode.
Watc hdog Func tion
The watchdog monitors μP activity via the Watchdog
RESET are asserted. To use the watchdog function,
connect WDI to a bus line or μP I/O line. If WDI
remains high or low for longer than the watchdog time-
are asserted (see RESET and –————Outputs section,
and the Watchdog Outputdiscussion on this page).
Watchdog Input
A change of state (high to low, low to high, or a mini-
mum 100ns pulse) at the Watchdog Input (WDI) during
the watchdog period resets the watchdog timer. The
watchdog default timeout is 1.6sec.
To disable the watchdog function, leave WDI floating.
An internal resistor network (100k
equivalent imped-
ance at WDI) biases WDI to approximately 1.6V.
Internal comparators detect this level and disable the
watchdog timer. When V
is below the reset thresh-
old, the watchdog function is disabled and WDI is dis-
connected from its internal resistor network, thus
becoming high impedance.
Watchdog Output
The Watchdog Output (–W——O) remains high if there is a
transition or pulse at WDI during the watchdog timeout
a logic high when V
is below the reset threshold, bat-
tery-backup mode is enabled, or WDI is an open circuit.
In watchdog mode, if no transition occurs at WDI during
–asserted for the reset timeout period (200ms typical).
at WDI (Figure 2). If WDI is held high or low indefinitely,
1.6sec. –W——Ohas a 2 x TTL output characteristic.
Selecting an Alternative
Watchdog and Reset Timeout Period
The OSC SEL and OSC IN inputs control the watchdog
and reset timeout periods. Floating OSC SEL and OSC
IN or tying them both to V
selects the nominal 1.6sec
watchdog timeout period and 200ms reset timeout peri-
od. Connecting OSC IN to GND and floating or connect-
ing OSC SEL to V
selects the 100ms normal
watchdog timeout delay and 1.6sec delay immediately
after reset. The reset timeout delay remains 200ms
(Figure 2). Select alternative timeout periods by con-
necting OSC SEL to GND and connecting a capacitor
between OSC IN and GND, or by externally driving OSC
IN (Table 1 and Figure 3). OSC IN is internally connect-
ed to a ±100nA (typ) current source that charges and
discharges the timing capacitor to create the oscillator
frequency, which sets the reset and watchdog timeout
periods (see Connecting a Timing Capacitor at OSC IN
in the Applications Informationsection).
Mic roproc essor S upervisory Circ uits
8
_______________________________________________________________________________________
MAX691A
MAX693A
TO
μ
P RESET
1k
15
RESET
WDI
WDO
RESET
t
1
t
1
t
3
t
2
t
1
= RESET TIMEOUT PERIOD
t
2
= NORMAL WATCHDOG TIMEOUT PERIOD
t
3
= WATCHDOG TIMEOUT PERIOD IMMEDIATELY AFTER RESET
Figure 1. Adding an external pull-down resistor ensures
CC
down to GND.
Figure 2. Watchdog Timeout Period and Reset Active Time
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX691AC/D | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX691ACPE | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX691ACPE+ | 功能描述:監(jiān)控電路 MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX691ACSE | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
| MAX691ACSE+ | 功能描述:監(jiān)控電路 MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數(shù): 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復(fù)位:Resettable 監(jiān)視器:No Watchdog 電池備用開關(guān):No Backup 上電復(fù)位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
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