December 1990 2
Philips Semiconductors Product specification
BCD to decimal decoder (1-of-10) 74HC/HCT42
FEATURES
• Mutually exclusive outputs
• 1-of-8 demultiplexing capability
• Outputs disabled for input codes above nine
• Output capability: standard
• I
CC
category: MSI
GENERAL DESCRIPTION
The 74HC/HCT42 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/HCT42 decoders accept four active HIGH BCD
inputs and provide 10 mutually exclusive active LOW
outputs. The active LOW outputs facilitate addressing
other MSI circuits with active LOW input enables.
The logic design of the “42” ensures that all outputs are
HIGH when binary codes greater than nine are applied to
the inputs.
The most significant input (A
3
) produces an useful inhibit
function when the “42” is used as a 1-of-8 decoder. The A
3
input can also be used as the data input in an 8-output
demultiplexer application.
QUICK REFERENCE DATA
GND = 0 V; T
amb
=25°C; t
r
=t
f
= 6 ns
Notes
1. C
PD
is used to determine the dynamic power dissipation (P
D
in µW):
P
D
=C
PD
× V
CC
2
× f
i
+∑(C
L
× V
CC
2
× f
o
) where:
f
i
= input frequency in MHz
f
o
= output frequency in MHz
∑ (C
L
× V
CC
2
× f
o
) = sum of outputs
C
L
= output load capacitance in pF
V
CC
= supply voltage in V
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
ORDERING INFORMATION
See
“74HC/HCT/HCU/HCMOS Logic Package Information”
.
SYMBOL PARAMETER CONDITIONS
TYPICAL
UNIT
HC HCT
t
PHL
/ t
PLH
propagation delay A
n
to Y
n
C
L
= 15 pF; V
CC
= 5 V 14 17 ns
C
I
input capacitance 3.5 3.5 pF
C
PD
power dissipation capacitance per package notes 1 and 2 37 37 pF
