Datasheet

September 1993 4
Philips Semiconductors Product specification
Dual retriggerable precision monostable
multivibrator
74HC/HCT4538
Fig.4 Functional diagram.
Fig.5 Connection of the external timing
components R
t
and C
t
.
(1) Connect C
TC
(pins 1 and 15) to GND (pin 8).
FUNCTION TABLE
Notes
1. H = HIGH voltage level
L = LOW voltage level
X = don’t care
↑ = LOW-to-HIGH transition
↓ = HIGH-to-LOW transition
= one HIGH level output pulse
= one LOW level output pulse
INPUTS OUTPUTS
nA
0
nA
1
nR
D
nQ nQ
↓ LH
H↑H
XXL LH
Fig.6 Timing diagram.
(1) Positive edge triggering.
(2) Positive edge retriggering (pulse
lengthening).
(3) Negative edge triggering.
(4) Reset (pulse shortening).
(5) V
ref1
and V
ref2
are internal reference voltages.
(6) T = 0.7 × R
t
× C
t
(see also Fig.5).