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參數(shù)資料
| 型號： | STM809LWX6F |
| 廠商： | 意法半導(dǎo)體 |
| 英文描述： | Reset Circuit |
| 中文描述： | 復(fù)位電路 |
| 文件頁數(shù)： | 6/18頁 |
| 文件大?。?/td> | 255K |
| 代理商： | STM809LWX6F |
STM809/810/811/812
6/18
OPERATION
Reset Output
The STM809/810/811/812 MICROPROCESSOR
RESET CIRCUIT asserts a reset signal to the
MCU whenever V
CC
goes below the reset thresh-
old (V
RST
), or when the push-button reset input
(MR) is taken low (see
Figure 15., page 11
). RST
(active high for STM810/812) is guaranteed valid
down to V
CC
= 1V (0° to 70°C).
During power-up, once V
CC
exceeds the reset
threshold an internal timer keeps RST low for the
reset time-out period, t
rec
. After this interval, RST
returns high.
If V
CC
drops below the reset threshold, RST goes
low. Each time RST is asserted, it stays low for at
least the reset time-out period. Any time V
CC
goes
below the reset threshold, the internal timer clears.
The reset timer starts when V
CC
returns above the
reset threshold. The active-low reset (RST) and
active-high reset (RST) both source and sink cur-
rent.
Push-Button Reset Input (STM811/812)
A logic low on MR asserts RST. RST remains as-
serted while MR is low, and for t
rec
after it returns
high. The MR input has an internal 20k
pull-up
resistor, allowing it to be left open if not used. This
input can be driven with TTL/CMOS-logic levels or
with open-drain/collector outputs. Connect a nor-
mally open push-button switch from MR to GND to
create a manual reset function; external debounce
circuitry is not required. If the device is used in a
noisy environment, connect a 0.1μF capacitor
from MR to GND to provide additional noise immu-
nity.
Negative-Going V
CC
Transients
The STM809/810/811/812 are relatively immune
to negative-going V
CC
transients (glitches).
Figure
13., page 9
shows typical transient duration ver-
sus reset comparator overdrive (for which the
STM809/810/811/812 will NOT generate a reset
pulse). The graph was generated using a negative
pulse applied to V
CC
, starting at 0.5V above the
actual reset threshold and ending below it by the
magnitude indicated (comparator overdrive). The
graph indicates the maximum pulse width a nega-
tive V
CC
transient can have without causing a re-
set pulse. As the magnitude of the transient
increases (further below the threshold), the maxi-
mum allowable pulse width decreases. Any com-
bination of duration and overdrive which lies under
the curve will NOT generate a reset signal. Typi-
cally, a V
CC
transient that goes 100mV below the
reset threshold and lasts 20μs or less will not
cause a reset pulse. A 0.1μF bypass capacitor
mounted as close as possible to the V
CC
pin pro-
vides additional transient immunity.
Valid /RST Output Down to V
CC
= 0V
When V
CC
falls below 1V, the RST (STM809/811)
output no longer sinks current, but becomes an
open circuit. In most systems this is not a problem,
as most MCUs do not operate below 1V. However,
in applications where RST output must be valid
down to 0V, a pull-down resistor may be added to
hold the RST output low. This resistor must be
large enough to not load the RST output, and still
be small enough to pull the output to ground. A
100K
resistor is recommended.
Note:
The same situation applies for the active-
high RST of the STM810/812. A 100K
pull-up re-
sistor to V
CC
should be used if RST must remain
valid for V
CC
< 1.0V.
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相關(guān)代理商/技術(shù)參數(shù) |
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| STM809MW16F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Reset Circuit |
| STM809MWX6F | 功能描述:監(jiān)控電路 4.38V Reset 140ms 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 |
| STM809MWX6F-CUT TAPE | 制造商:ST 功能描述:STM809 Series 4.38 V 140 ms Surface Mount Reset Circuit - SOT-23 |
| STM809RW16F | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:Reset Circuit |
| STM809RWX6F | 功能描述:監(jiān)控電路 2.63V Reset 140ms 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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