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參數(shù)資料
| 型號： | ADM8690-ADM8695 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Microprocessor Supervisory Circuits |
| 中文描述： | 微處理器監(jiān)控電路 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大小： | 183K |
| 代理商： | ADM8690-ADM8695 |
ADM8690–ADM8695
REV. 0
–12–
RESET
Output
T he internal voltage detector monitors V
CC
and generates a
RESET
output to hold the microprocessor’s Reset line low
when V
CC
is below 4.65 V (4.4 V for ADM8693). An internal
timer holds
RESET
low for 50 ms (200 ms for the ADM8695)
after V
CC
rises above 4.65 V (4.4 V for ADM8693). T his pre-
vents repeated toggling of
RESET
even if the 5 V power drops
out and recovers with each power line cycle.
T he crystal oscillator normally used to generate the clock for
microprocessors can take several milliseconds to stabilize. Since
most microprocessors need several clock cycles to reset,
RESET
must be held low until the microprocessor clock oscillator has
started. T he power-up
RESET
pulse lasts 50 ms (200 ms for the
ADM8695) to allow for this oscillator start-up time. If a differ-
ent reset pulse width is required, then a capacitor should be
connected to OSC IN or an external clock may be used. Please
refer to T able I and Figure 4. T he manual reset switch and the
0.1
μ
F capacitor connected to the reset line can be omitted if a
manual reset is not needed. An inverted, active high, RESET
output is also available.
Power Fail Detector
T he +5 V V
CC
power line is monitored via a resistive potential
divider connected to the Power Fail Input (PFI). When the
voltage at PFI falls below 1.3 V, the Power Fail Output (
PFO
)
drives the processor’s NMI input low. If for example a Power
Fail threshold of 4.8 V is set with resistors R
1
and R
2
, the micro-
processor will have the time when V
CC
falls from 4.8 V to 4.65 V
to save data into RAM. An earlier power fail warning can be gen-
erated if the unregulated dc input to the 5 V regulator is avail-
able for monitoring. T his will allow more time for micro-
processor housekeeping tasks to be completed before power is
lost.
RAM Write Protection
T he ADM8691/ADM8693/ADM8695
CE
OUT
line drives the
Chip Select inputs of the CMOS RAM.
CE
OUT
follows
CE
IN
as
long as V
CC
is above the 4.65 V (4.4 V for ADM8693) reset
threshold.
If V
CC
falls below the reset threshold,
CE
OUT
goes high, inde-
pendent of the logic level at
CE
IN
. T his prevents the micropro-
cessor from writing erroneous data into RAM during power-up,
power-down, brownouts and momentary power interruptions.
Watchdog T imer
T he microprocessor drives the Watchdog Input (WDI) with an
I/O line. When OSC IN and OSC SEL are unconnected, the
microprocessor must toggle the WDI pin once every 1.6 seconds
to verify proper software execution. If a hardware or software
failure occurs such that WDI is not toggled, the ADM8691/
ADM8693 will issue a 50 ms (200 ms for ADM8695)
RESET
pulse after 1.6 seconds. T his typically restarts the micro-
processor’s power-up routine. A new
RESET
pulse is issued
every 1.6 seconds until WDI is again strobed. If a different
watchdog timeout period is required, then a capacitor should be
connected to OSC IN or an external clock may be used. Please
refer to T able I and Figure 4.
T he Watchdog Output (
WDO
) goes low if the watchdog timer
is not serviced within its timeout period. Once
WDO
goes low,
it remains low until a transition occurs at WDI. T he watchdog
timer feature can be disabled by leaving WDI unconnected.
T he
RESET
output has an internal 3
μ
A pull-up, and can either
connect to an open collector reset bus or directly drive a CMOS
gate without an external pull-up resistor.
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| ADM8690 | Microprocessor Supervisory Circuits(微處理器監(jiān)控電路) |
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| ADM8690AN | 功能描述:IC SUPERVISOR MPU 4.65V 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型:簡單復(fù)位/加電復(fù)位 監(jiān)視電壓數(shù)目:1 輸出:開路漏極或開路集電極 復(fù)位:高有效 復(fù)位超時:- 電壓 - 閥值:1.8V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:6-TSOP（0.059"，1.50mm 寬）5 引線 供應(yīng)商設(shè)備封裝:5-TSOP 包裝:剪切帶 (CT) 其它名稱:NCP301HSN18T1GOSCT |
| ADM8690ANZ | 功能描述:IC SUPERVISOR MPU 4.65V 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - 監(jiān)控器 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 類型:簡單復(fù)位/加電復(fù)位 監(jiān)視電壓數(shù)目:1 輸出:開路漏極或開路集電極 復(fù)位:高有效 復(fù)位超時:- 電壓 - 閥值:1.8V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:6-TSOP（0.059"，1.50mm 寬）5 引線 供應(yīng)商設(shè)備封裝:5-TSOP 包裝:剪切帶 (CT) 其它名稱:NCP301HSN18T1GOSCT |
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