1 Features
• Select one of eight data outputs:
– Active low for '138
– Active high for '238
• l/O port or memory selector
• Three enable inputs to simplify cascading
• Typical propagation delay of 13 ns at VCC = 5 V, CL
= 15 pF, TA = 25°C
• Fanout (over temperature range)
– Bus driver outputs: 15 LSTTL loads
– Standard outputs: 10 LSTTL loads
• Wide operating temp range: -55°C to 125°C
• Balanced propagation delay and transition times
• Significant power reduction compared to LSTTL
logic ICs
• HC types
– 2 V to 6 V operation
– High noise immunity: NIL = 30%, NIH = 30% of
VCC at VCC = 5 V
• HCT types
– 4.5-V to 5.5-V operation
– Direct LSTTL input logic compatibility, VIL= 0.8
V (Max), VIH = 2 V (Min)
– CMOS input compatibility, Il ≤ 1μA at VOL, VOH

2 Description
The CDx4HC(T)138 and '238 are three to eight
decoders with one standard output strobe (G2) and
two active low output strobes (G 1 and G 0). When the
outputs are gated by any of the strobe inputs, they are
all forced into the high state. When the outputs are not
disabled by the strobe inputs, only the selected output
is low while all others are high.
The CDx4HC(T)238 is a three to eight decoder with
one standard output strobe (G2) and two active low
output strobes (G 1 and G 0). When the outputs are
gated by any of the strobe inputs, they are all forced
into the low state. When the outputs are not disabled
by the strobe inputs, only the selected output is high
while all others are low.