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參數資料
| 型號： | MCP809M3-4.00 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 電源管理 |
| 英文描述： | 3-Pin Microprocessor Reset Circuits |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO3 |
| 封裝： | SOT-23, 3 PIN |
| 文件頁數： | 6/7頁 |
| 文件大小： | 151K |
| 代理商： | MCP809M3-4.00 |
Applications Information
Benefits of Precision Reset Thresholds
A microprocessor supply supervisor must provide a reset
output within a predictable range of the supply voltage. A
common threshold range is between 5% and 10% below the
nominal supply voltage. The 4.63V and 3.08V options of the
MCP809/810 use highly accurate circuitry to ensure that the
reset threshold occurs only within this range (for 5V and 3.3V
supplies). The other voltage options have the same tight
tolerance to ensure a reset signal for other narrow monitor
ranges. See Table 1 for examples of how the standard reset
thresholds apply to 3V, 3.3V, and 5V nominal supply volt-
ages.
TABLE 1. Reset Thresholds Related to Common
Supply Voltages
Reset
Threshold
4.63
±
3%
4.38
±
3%
4.00
±
3%
3.08
±
3%
2.93
±
3%
2.63
±
3%
3.0V
3.3V
5.0V
90 - 95%
85 - 90%
78 - 82%
90 - 95%
86 - 90%
77 - 81%
85 - 90%
Ensuring a Valid Reset Output Down to V
CC
= 0V
When V
CC
falls below 1V, the MCP809 RESET output no
longer sinks current. A high-impedance CMOS logic input
connected to RESET can therefore drift to undetermined
voltages. To prevent this situation, a 100k
resistor should
be connected from the RESET output to ground, as shown in
Figure 1
A 100k
pull-up resistor to V
is also recommended for the
MCP810, if RESET is required to remain valid for V
CC
<
1V.
Negative-Going V
CC
Transients
The
MCP809/810
negative-going transients or glitches on V
. Figure 2shows
the maximum pulse width a negative-going V
CC
transient
are
relatively
immune
to
short
can have without causing a reset pulse. In general, as the
magnitude of the transient increases, going further below the
threshold, the maximum allowable pulse width decreases.
Typically,
for
the
4.63V
and
MCP809/810, a V
CC
transient that goes 100mV below the
reset threshold and lasts 20μs or less will not cause a reset
pulse. A 0.1 μF bypass capacitor mounted as close as
possible to the V
CC
pin will provide additional transient re-
jection.
4.38V
version
of
the
Interfacing to μPs with Bidirectional Reset Pins
Microprocessors with bidirectional reset pins, such as the
Motorola 68HC11 series, can be connected to the MCP809
RESET output. To ensure a correct output on the MCP809
even when the microprocessor reset pin is in the opposite
state, connect a 4.7k
resistor between the MCP809 RE-
SET output and the μP reset pin, as shown in Figure 3
Buffer the MCP809 RESET output to other system compo-
nents.
20022310
FIGURE 1. RESET Valid to V
CC
= Ground Circuit
20022309
FIGURE 2. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Comparator
Overdrive
20022311
FIGURE 3. Interfacing to Microprocessors with
Bidirectional Reset I/O
M
www.national.com
6
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相關代理商/技術參數 |
參數描述 |
|---|---|
| MCP809M3463 | 制造商:NATIONAL 功能描述:New |
| MCP809M3X-2.63 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3-Pin Microprocessor Reset Circuits |
| MCP809M3X-2.93 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3-Pin Microprocessor Reset Circuits |
| MCP809M3X-3.08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:3-Pin Microprocessor Reset Circuits |
| MCP809M3X-3.08/NOPB | 制造商:Texas Instruments 功能描述:Processor Supervisor 3.08V 3V/3.3V/5V 3-Pin SOT-23 T/R |
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