INTEGRATED CIRCUITS
DATA SHEET
For a complete data sheet, please also download:
•
The IC06 74HC/HCT/HCU/HCMOS Logic Family Specifications
•
The IC06 74HC/HCT/HCU/HCMOS Logic Package Information
•
The IC06 74HC/HCT/HCU/HCMOS Logic Package Outlines
74HC/HCT423
Dual retriggerable monostable
multivibrator with reset
Product specification
Supersedes data of December 1990
File under Integrated Circuits, IC06
1998 Jul 08
Philips Semiconductors
Product specification
Dual retriggerable monostable
multivibrator with reset
FEATURES
•
DC triggered from active HIGH or active LOW inputs
•
Retriggerable for very long pulses up to 100% duty
factor
•
Direct reset terminates output pulse
•
Schmitt-trigger action on all inputs except for the reset
input
•
Output capability: standard (except for nR
EXT
/C
EXT
)
•
I
CC
category: MSI
GENERAL DESCRIPTION
The 74HC/HCT423 are high-speed Si-gate CMOS devices
and are pin compatible with low power Schottky TTL
(LSTTL). They are specified in compliance with JEDEC
standard no. 7A.
The 74HC/HCT423 are dual retriggerable monostable
multivibrators with output pulse width control by two
methods. The basic pulse time is programmed by
selection of an external resistor (R
EXT
) and capacitor
74HC/HCT423
(C
EXT
). The external resistor and capacitor are normally
connected as shown in Fig.6.
Once triggered, the basic output pulse width may be
extended by retriggering the gated active LOW-going edge
input (nA) or the active HIGH-going edge input (nB). By
repeating this process, the output pulse period
(nQ = HIGH, nQ = LOW) can be made as long as desired.
When nR
D
is LOW, it forces the nQ output LOW, the
nQ output HIGH and also inhibits the triggering.
Figures 7 and 8 illustrate pulse control by reset. The basic
output pulse width is essentially determined by the values
of the external timing components R
EXT
and C
EXT
.
For pulse widths, when C
EXT
<
10 000 pF, see Fig.9.
When C
EXT
>
10 000 pF, the typical output pulse width is
defined as:
t
W
= 0.45
×
R
EXT
×
C
EXT
(typ.),
where, t
W
= pulse width in ns;
R
EXT
= external resistor in kΩ;
C
EXT
= external capacitor in pF.
Schmitt-trigger action in the nA and nB inputs, makes the
circuit highly tolerant to slower input rise and fall times.
The “423” is identical to the “123” but cannot be triggered
via the reset input.
QUICK REFERENCE DATA
GND = 0 V; T
amb
= 25
°C;
t
r
= t
f
= 6 ns
SYMBOL
t
PHL
/ t
PLH
PARAMETER
propagation delay
nA, nB to nQ, nQ
nR
D
to nQ, nQ
C
I
t
W
Notes
input capacitance
minimum output pulse width nQ, nQ
TYPICAL
CONDITIONS
HC
C
L
= 15 pF; V
CC
= 5 V;
R
EXT
= 5 kΩ; C
EXT
= 0 pF
25
20
3.5
notes 1 and 2
75
26
22
3.5
75
HCT
ns
ns
pF
ns
UNIT
1. C
PD
is used to determine the dynamic power dissipation (P
D
in
µW):
P
D
= C
PD
×
V
CC2
×
f
i
+ ∑
(C
L
×
V
CC2
×
f
o
)
+
0.75
×
C
EXT
×
V
CC2
×
f
o
+
D
×
16
×
V
CC
where:
f
i
= input frequency in MHz
f
o
= output frequency in MHz
D = duty factor in %
∑
(C
L
×
V
CC2
×
f
o
) = sum of outputs
C
L
= output load capacitance in pF
V
CC
= supply voltage in V
C
EXT
= timing capacitance in pF
2. For HC the condition is V
I
= GND to V
CC
For HCT the condition is V
I
= GND to V
CC
−
1.5 V
1998 Jul 08
2
Philips Semiconductors
Product specification
Dual retriggerable monostable
multivibrator with reset
ORDERING INFORMATION
TYPE
NUMBER
74HC423N;
74HCT423N
74HC423D;
74HCT423D
PIN DESCRIPTION
PIN NO.
1, 9
2, 10
3, 11
4, 12
7
8
13, 5
14, 6
15
16
SYMBOL
1A, 2A
1B, 2B
1R
D
, 2R
D
1Q, 2Q
2R
EXT
/C
EXT
GND
1Q, 2Q
1C
EXT
, 2C
EXT
1R
EXT
/C
EXT
V
CC
NAME AND FUNCTION
trigger inputs (negative-edge triggered)
trigger inputs (positive-edge triggered)
direct reset action (active LOW)
outputs (active LOW)
external resistor/capacitor connection
ground (0 V)
outputs (active HIGH)
external capacitor connection
external resistor/capacitor connection
positive supply voltage
PACKAGE
NAME
DIP16
SO16
DESCRIPTION
plastic dual in-line package; 16 leads (300 mil); long body
plastic small outline package; 16 leads; body width 3.9 mm;
low stand-off height
74HC/HCT423
VERSION
SOT38-1
SOT109-1
Fig.1 Pin configuration.
Fig.2
Fig.3 IEC logic symbol.
1998 Jul 08
3
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