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 (I0), an active HIGH
trigger/retrigger input (I1), an overriding active LOW direct
reset input (CD), an output (O) and its complement (O),
and two pins (CTC,
(1)
RCTC) for connecting the external
timing components Ctand Rt. 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 Rt.
The output pulse width (T) is equal to Rt× Ct. The linear
design techniques in LOCMOS guarantee precise control
of the output pulse width.
A LOW level at CDterminates 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,I0B
input (HIGH to LOW triggered)
I
1A
, I
1B
input (LOW to HIGH triggered)
CDA, C
DB
direct reset input (active LOW)
O
A
, O
B
output
OA, 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.