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參數資料
| 型號： | MAX825 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Parallel-Load 8-Bit Shift Registers 16-CDIP -55 to 125 |
| 中文描述： | 5引腳、微處理器監(jiān)控電路，帶有看門狗定時器及手動復位 |
| 文件頁數： | 7/8頁 |
| 文件大?。?/td> | 78K |
| 代理商： | MAX825 |
Interfac ing to μPs with
Bidirec tional Reset Pins
The
RESET
output maximum pull-up current is 800μA
for L/M versions (400μA for T/S/R versions). This allows
μPs with bidirectional resets, such as the 68HC11, to
force
RESET
low when the MAX823/MAX824/MAX825
are pulling
RESET
high (Figure 4).
Negative-Going V
CC
T ransients
These supervisors are relatively immune to short-
duration, negative-going V
CC
transients (glitches), which
usually do not require the entire system to shut down.
Resets are issued to the μP during power-up, power-
down, and brownout conditions.
The Typical Operating Characteristics show a graph of
the MAX823L’s Maximum V
CC
Transient Duration vs.
Reset Threshold Overdrive, for which reset pulses are
not
generated. The graph was produced using nega-
tive-going V
CC
pulses, starting at 5V and ending below
the reset threshold by the magnitude indicated (reset
threshold overdrive). The graph shows the maximum
pulse width that a negative-going V
CC
transient can
typically have without triggering a reset pulse. As the
amplitude of the transient increases (i.e., goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Typically, a V
CC
transient that
goes 100mV below the reset threshold and lasts for
15μs or less will not trigger a reset pulse.
An optional 0.1μF bypass capacitor mounted close to
V
CC
provides additional transient immunity.
Watc hdog S oftware Considerations
(MAX 823/MAX 824)
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
input at different points in the program, rather than
pulsing the watchdog input high-low-high or low-high-
low. This technique avoids a stuck loop, in which the
watchdog timer would continue to be reset inside the
loop, keeping the watchdog from timing out.
Figure 5 shows an example of a flow diagram where the
I/O driving the watchdog input is set high at the begin-
ning of the program, set low at the beginning of every
subroutine or loop, then set high again when the pro-
gram returns to the beginning. If the program should
hang in any subroutine, the problem would quickly be
corrected, since the I/O is continually set low and the
watchdog timer is allowed to time out, causing a reset
or interrupt to be issued. As described in the Watchdog
Input Currentsection, this scheme results in higher time
average WDI input current than does leaving WDI low
for the majority of the timeout period and periodically
pulsing it low-high-low.
M
5-Pin Mic roproc essor S upervisory Circ uits
_______________________________________________________________________________________
7
MAX823
MAX824
MAX825
μ
P
V
CC
V
CC
V
CC
GND
GND
RESET
I
SOURCE
MAX = 800
μ
A L, M
400
μ
A T, S, R
RESET
GENERATOR
Figure 4. Interfacing to μPs with Bidirectional Resets
START
SET WDI
HIGH
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
RETURN
Figure 5. Watchdog Flow Diagram
相關PDF資料 |
PDF描述 |
|---|---|
| MAX825_EUK | Parallel-Load 8-Bit Shift Registers 20-LCCC -55 to 125 |
| MAX836EUS-T | 4-Pin Micropower Voltage Monitors |
| MAX837 | 4-Pin Micropower Voltage Monitors |
| MAX836-MAX837 | 4-Pin Micropower Voltage Monitors |
| MAX836 | 4-Pin Micropower Voltage Monitors |
相關代理商/技術參數 |
參數描述 |
|---|---|
| MAX825_EUK | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:5-Pin Microprocessor Supervisory Circuits |
| MAX825L | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:5-Pin Microprocessor Supervisory Circuits With Watchdog Timer and Manual Reset |
| MAX825LEUK | 制造商:Maxim Integrated Products 功能描述: 制造商:Maxim Integrated Products 功能描述:- Bulk |
| MAX825LEUK+ | 制造商:Maxim Integrated Products 功能描述: 制造商:Maxim Integrated Products 功能描述:PROCESSOR SUPERVISOR 4.63V 4.5UA 5PIN SOT-23 - Rail/Tube 制造商:Maxim Integrated Products 功能描述:uP supervisory circuits, MAX825LEUK+ 制造商:Maxim Integrated Products 功能描述:MAX825LEUK+ |
| MAX825LEUK+T | 功能描述:監(jiān)控電路 5-Pin MPU Supervisor RoHS:否 制造商:STMicroelectronics 監(jiān)測電壓數: 監(jiān)測電壓: 欠電壓閾值: 過電壓閾值: 輸出類型:Active Low, Open Drain 人工復位:Resettable 監(jiān)視器:No Watchdog 電池備用開關:No Backup 上電復位延遲（典型值）:10 s 電源電壓-最大:5.5 V 最大工作溫度:+ 85 C 安裝風格:SMD/SMT 封裝 / 箱體:UDFN-6 封裝:Reel |
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