74HC4538 查看數據表（PDF） - Nexperia B.V. All rights reserved
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74HC4538 Datasheet PDF : 21 Pages
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Nexperia
74HC4538
Dual retriggerable precision monostable multivibrator
6 Functional description
Table 3. Function table [1]
Inputs
nA
nB
↓
L
H
↑
X
X
nCD
H
H
L
Outputs
nQ
nQ
L
H
[1] H = HIGH voltage level; L = LOW voltage level; X = don’t care;
↑ = positive-going transition; ↓ = negative-going transition;
= one HIGH level output pulse, with the pule width determined by CEXT and REXT;
= one LOW level output pulse, with the pulse width determined by CEXT and REXT.
(1)
nB input
(3)
nA input
nCD input
nREXT/CEXT input
Vref1
Vref2
nQ output
T
T
(5)
(1) Positive edge triggering.
(2) Positive edge re-triggering (pulse lengthening).
(3) Negative edge triggering.
(4) Reset (pulse shortening).
(5) TW = 0.7 x REXT x CEXT (see also Figure 6.
Figure 5. Timing diagram
(1)
(2)
(1)
(4)
Vref1
Vref2
T
001aae737
GND
CEXT
REXT
VCC
nCEXT
nREXT/CEXT
nA
nQ
T
nB
nQ T = 0.7 × REXT × CEXT
nCD
001aak192
Figure 6. Connection of the external timing components REXT and CEXT
74HC4538
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 5 — 17 March 2017
© Nexperia B.V. 2017. All rights reserved.
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