January 1995 2
Philips Semiconductors Product specification
Dual precision monostable multivibrator
HEF4538B
MSI
DESCRIPTION
The HEF4538B is a dual retriggerable-resettable
monostable multivibrator. Each multivibrator has an active
LOW trigger/retrigger input (I
0
), an active HIGH
trigger/retrigger input (I
1
), an overriding active LOW direct
reset input (C
D
), an output (O) and its complement (O),
and two pins (C
TC
,
(1)
RC
TC
) for connecting the external
timing components C
t
and R
t
. Typical pulse width variation
over temperature range is ± 0,2%.
The HEF4538B may be triggered by either the positive or
the negative edges of the input pulse and will produce an
accurate output pulse with a pulse width range of 10 µs to
infinity. The duration and accuracy of the output pulse are
determined by the external timing components C
t
and R
t
.
The output pulse width (T) is equal to R
t
× C
t
. The linear
design techniques in LOCMOS guarantee precise control
of the output pulse width.
A LOW level at C
D
terminates the output pulse
immediately. Schmitt-trigger action in the trigger inputs
makes the circuit highly tolerant to slower rise and fall
times.
Fig.1 Functional diagram.
PINNING
Note
1. Always connected to ground.
FAMILY DATA, I
DD
LIMITS category MSI
See Family specifications.
HEF4538BP(N): 16-lead DIL; plastic (SOT38-1)
HEF4538BD(F): 16-lead DIL; ceramic (cerdip) (SOT74)
HEF4538BT(D): 16-lead SO; plastic (SOT109-1)
( ): Package Designator North America
I
0A,
I
0B
input (HIGH to LOW triggered)
I
1A
, I
1B
input (LOW to HIGH triggered)
C
DA
, C
DB
direct reset input (active LOW)
O
A
, O
B
output
O
A
, O
B
complementary output (active LOW)
C
TC A
, C
TC B
external capacitor connections
(1)
RC
TC A
, RC
TC B
external capacitor/ resistor
connections
Fig.2 Pinning diagram.
