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參數(shù)資料
| 型號： | TC74VHC221AFK |
| 廠商： | Toshiba Corporation |
| 英文描述： | Dual Monostable Multivibrator |
| 中文描述： | 雙單穩(wěn)態(tài)觸發(fā)器 |
| 文件頁數(shù)： | 6/15頁 |
| 文件大小： | 323K |
| 代理商： | TC74VHC221AFK |
TC74VHC123,221AF/AFN/AFT/AFK
2007-10-19
6
Functional Description
(1)
Standby state
The external capacitor (C
X
) is fully charged to V
CC
in the stand-by state. That means, before
triggering, the Q
P
and Q
N
transistors which are connected to the R
X
/C
X
node are in the off state. Two
comparators that relate to the timing of the output pulse, and two reference voltage supplies turn off.
The total supply current is only leakage current.
Trigger operation
Trigger operation is effective in any of the following three cases. First, the condition where the
A
input is low, and the B input has a rising signal; second, where the B input is high, and the A input
has a falling signal; and third, where the A input is low and the B input is high, and the
CLR
input has a rising signal.
After a trigger becomes effective, comparators C
1
and C
2
start operating, and Q
N
is turned on. The
external capacitor discharges through Q
N
. The voltage level at the R
X
/C
X
node drops. If the R
X
/C
X
voltage level falls to the internal reference voltage V
ref
L, the output of C
1
becomes low. The flip-flop is
then reset and Q
N
turns off. At that moment C
1
stops but C
2
continues operating.
After Q
N
turns off, the voltage at the R
X
/C
X
node starts rising at a rate determined by the time
constant of external capacitor C
X
and resistor R
X
.
Upon triggering, output Q becomes high, following some delay time of the internal F/F and gates. It
stays high even if the voltage of R
X
/C
X
changes from falling to rising. When R
X
/C
X
reaches the
internal reference voltage V
ref
H, the output of C
2
becomes low, the output Q goes low and C
2
stops its
operation. That means, after triggering, when the voltage level of the R
X
/C
X
node reaches V
ref
H, the
IC returns to its MONOSTABLE state.
With large values of C
X
and R
X
, and ignoring the discharge time of the capacitor and internal
delays of the IC, the width of the output pulse, t
w (OUT)
, is as follows:
t
w (OUT)
= 1.0 · C
X
· R
X
Retrigger operation (TC74VHC123A)
When a new trigger is applied to either input A or B while in the MONOSTABLE state, it is
effective only if the IC is charging C
X
. The voltage level of the R
X
/C
X
node then falls to V
ref
L level
again. Therefore the Q output stays high if the next trigger comes in before the time period set by C
X
and R
X
.
If the new trigger is very close to previous trigger, such as an occurrence during the discharge cycle,
it will have no effect.
The minimum time for a trigger to be effective 2nd trigger, trr (min.), depends on VCC and CX.
Reset operation
In normal operation, the
CLR
input is held high. If
CLR
is low, a trigger has no effect because
the Q output is held low and the trigger control F/F is reset. Also, Q
P
turns on and C
X
is charged
rapidly to V
CC
.
This means if
CLR
is set low, the IC goes into a wait state.
(2)
(3)
(4)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TC74VHC221AFK(EL,K | 制造商:Toshiba America Electronic Components 功能描述:Logic,TC74VHC,MonoStable Multivbrtr,US16 |
| TC74VHC221AFN | 制造商:Toshiba America Electronic Components 功能描述:MONOSTABLE MULTIVIBRATOR DUAL 16PIN SOL - Tape and Reel |
| TC74VHC221-AFT | 制造商:Toshiba America Electronic Components 功能描述: |
| TC74VHC221AFT(EK2M | 功能描述:單穩(wěn)態(tài)多諧振蕩器 CMOS LOGIC IC STD LOGIC IC’S RoHS:否 制造商:Texas Instruments 每芯片元件:1 邏輯系列:LVC 邏輯類型:Monostable Multivibrator 封裝 / 箱體:SSOP-8 傳播延遲時間:18.6 ns 高電平輸出電流:- 32 mA 低電平輸出電流:32 mA 電源電壓-最大:5.5 V 電源電壓-最小:1.65 V 最大功率耗散: 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝:Reel |
| TC74VHC221AFT(EL,K | 制造商:Toshiba America Electronic Components 功能描述:Logic,C-MOS,74VHC,TC74VHC221AFT |
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