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参数资料
| 型号： | M54HC4538 |
| 厂商： | 意法半导体 |
| 英文描述： | Dual Retriggerable Monostable Multivibrator(双可再触发单稳态多谐振荡器) |
| 中文描述： | 双Retriggerable单稳态触发器（双可再触发单稳态多谐振荡器） |
| 文件页数： | 3/14页 |
| 文件大小： | 288K |
| 代理商： | M54HC4538 |
BLOCK DIAGRAM
Notes :
1. Cx, Rx,Dx areexternal components.
2. Dx isa clamping diode.
3. The external capacitor is charged to V
CC
inthe stand-by state,i.e. no trigger.Whenthe supply voltage isturned offCx is discharged
mainlythrough aninternalparasitic diode(seefigures). IfCxissufficientlylargeandV
CC
decreases rapidy, there willbesomepossibility
of damagng the I.C.witha surgecurrent or latch-up.If the voltage supplyfiltercapacitor is largeenough and V
CC
decrease slowly,
thesurgecurrent is automatically limitedand damage theI.C.is avoided. Themaximum forwardcurrent of theparasitic diodeis ap-
proximately 20 mA.In cases where Cx is largethe time taken for the supply voltageto fallto 0.4V
CC
can be calculated asfollows :
t
f
≥
(V
CC
–0.7)
Cx/20mA
In caseswhere t
f
istooshort an external champng diodeisrequired to protect the I.C. from thesurge current.
FUNCTIONAL DESCRIPTION
STAND-BY STATE
The external capacitor, Cx, is fully charged to V
CC
inthe stand-bystate.Hence, before triggering, tran-
sistorQpandQn (connected tothe Rx/Cxnode) are
bothturnedoff.Thetwocomparatorsthatcontrolthe
timing and the two reference voltage sources stop
operating. The total supply current is therefore only
leakage current.
TRIGGEROPERATION
Triggering occurswhen :
1 st)A is”low” and B has a falling edge ;
2 nd) B is ”high” and A has a rising edge ;
After the multivibrator has been retriggered com-
paratorC1 and C2 start operating and Qn isturned
on. Cx then discharges through Qn. The voltage at
the node Rx/Cx external falls.
Whenitreaches V
REFL
theoutput of comparator C1
becomeslow. Thisinturnresets theflip-flop andQn
is turnedoff.
At this point C1 stops functioning but C2 continues
tooperate.ThevoltageatR/Cexternal beginstorise
with a timeconstant setbytheexternal components
Rx, Cx.
Triggering the multivibratorcausesQtogohigh after
internal delay due to the flip-flop and the gate. Qre-
mains high until the voltage at R/C external rises
againto V
REFH
. Atthis point C2output goeslowand
G goes low. C2 stops operating. That means that
aftertriggering when thevoltage at R/Cexternal re-
turns to V
REFH
the multivibrator has returned to its
MONOSTABLE STATE. In the case where Rx
Cx
are large enoughand the discharge time of the ca-
pacitorand thedelay timein theI.C.can be ignored,
the width of the output pulse tw (out) is as follows :
t
W(OUT)
= 0.72 Cx
Rx
RE-TRIGGEROPERATION
When a second trigger pulse follows the firstits ef-
fect will depend on the state of the multivibrator. If
the capacitor Cx is being charged the voltage level
of Rx/Cxexternalfalls toV
REFL
againandQremains
high i.e. the retrigger pulse arrives in a timeshorter
than the period Rx
Cx seconds, the capacitor
charging time constant. If the second trigger pulse
is veryclose totheinitial trigger pulse itis ineffective
; i.e.,the second trigger must arrive in the capacitor
discharge cycle to be ineffective.
Hence the minimum time fora second trigger to be
effective, trr (Min.) depends onV
CC
and Cx.
M54/M74HC4538
3/14
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相关代理商/技术参数 |
参数描述 |
|---|---|
| M54HC4538_04 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:RAD HARD DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR |
| M54HC4538D | 制造商:STMicroelectronics 功能描述:LOGIC, 5VOLTSMONOSTABLEDUAL MONOSTABLE MULTIVIBRATORDIL-16 S - Bulk |
| M54HC4538D1 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:RAD HARD DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR |
| M54HC4538F1R | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR |
| M54HC4538K | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:RAD HARD DUAL RETRIGGERABLE MONOSTABLE MULTIVIBRATOR |
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