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參數(shù)資料
| 型號(hào)： | MAX821-MAX822 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | 4-Pin レP Voltage Monitors with Pin-Selectable Power-On Reset Timeout Delay |
| 中文描述： | 4引腳レP的電壓監(jiān)視器的引腳可選上電復(fù)位延遲時(shí)間 |
| 文件頁數(shù)： | 5/8頁 |
| 文件大小： | 77K |
| 代理商： | MAX821-MAX822 |
_______________Detailed Desc ription
Reset Output
A microprocessor’s (μP’s) reset input starts the μP in a
known state. These
μ
P supervisory circuits assert reset
to prevent code-execution errors during power-up,
power-down, or brownout conditions. They also provide
a reset timeout delay that is pin programmable to 1ms
(max), 20ms (min), or 100ms (min). This feature allows
flexibility in designing bar-code scanners, hand-held
devices, and other applications that require quick or
nonstandard power-up times.
The MAX821’s
RESET
output is guaranteed to be a
logic low for V
CC
> 1V. Once V
CC
exceeds the reset
threshold, an internal timer keeps
RESET
low for the
reset timeout period, as determined by the Set Reset
Timeout (SRT) input. See the
Setting the Reset Timeout
Delay
section.
If a brownout condition occurs (V
CC
dips below the
reset threshold),
RESET
goes low. Any time V
CC
goes
below the reset threshold, the internal timer resets to
zero, and
RESET
goes low. The internal timer begins
counting after V
CC
returns above the reset threshold,
and
RESET
remains low for the reset timeout period.
The MAX822 has an active-high RESET output that is
the inverse of the MAX821’s
RESET
output.
S etting the Reset T imeout Delay
Use the three-level Set Reset Timeout (SRT) input to set
the reset timeout delay. Connect SRT to GND for a 1ms
(max) delay; connect it to V
CC
for a 20ms (min) delay;
or leave it unconnected for a 100ms (min) delay.
If you choose to drive the SRT pin with an external sig-
nal, make sure the signal source can charge/discharge
the capacitance on SRT quickly enough (<500μs) to
avert an unintended reset timeout delay.
To ensure proper operation when selecting the 100ms
timeout (SRT = unconnected), minimize capacitive
loading on the SRT pin (< 200pF). Excessive capacitive
loading can select an unintended faster timeout mode.
Reset T hreshold Ac c urac y
The MAX821/MAX822 are designed to meet their worst-
case specifications over their entire operating tempera-
ture range. Choose a reset threshold guaranteed to
assert at a voltage below the power supply’s regulation
range and above the minimum specified operating volt-
age range for the system’s ICs.
__________Applic ations Information
Negative-Going V
CC
T ransients
While designed to issue a reset to the microprocessor
(μP) during power-up, power-down, and brownout con-
ditions, the MAX821/MAX822 are relatively immune to
short-duration, negative-going V
CC
transients (glitches).
Figure 1 shows the maximum transient duration vs. reset
comparator overdrive for which the MAX821/MAX822
typically do not generate a reset pulse. This graph was
generated using a negative-going pulse applied to V
CC
,
starting above the actual reset threshold and ending
below it by the magnitude indicated (reset comparator
overdrive). The graph indicates the typical maximum
pulse width a negative-going V
CC
transient may have
without causing a reset pulse to be issued. As the mag-
nitude of the transient increases (goes farther below the
reset threshold), the maximum allowable pulse width
decreases. Typically, for the MAX821/MAX822, a V
CC
transient that goes 100mV below the reset threshold and
lasts 12μs or less will not cause a reset pulse to be
issued. A 0.1μF capacitor mounted as close as possible
to V
CC
can provide additional transient immunity, if
desired.
M
4-Pin μP Voltage Monitors with Pin-S elec table
Power-On Reset T imeout Delay
_______________________________________________________________________________________
5
300
250
0
1
10
100
1000
50
M
RESET COMPARATOR OVERDRIVE, V
TH
-V
CC
(mV)
M
μ
s
100
150
200
T
A
= +25
°
C
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Comparator Overdrive
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX821MUS | 制造商:Maxim Integrated Products 功能描述:4-PIN UP VOLTAGE MONITORS WITH PIN- - Rail/Tube |
| MAX821MUS+ | 制造商:Maxim Integrated Products 功能描述:PROCESSOR SUPERVISOR 4.38V 7UA 4PIN SOT-143 - Rail/Tube |
| MAX821MUS+T | 功能描述:監(jiān)控電路 4-Pin uPower Voltage Monitor RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)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 |
| MAX821MUST | 制造商:MAXIM 功能描述:Pb Free |
| MAX821MUS-T | 功能描述:監(jiān)控電路 RoHS:否 制造商:STMicroelectronics 監(jiān)測(cè)電壓數(shù): 監(jiān)測(cè)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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