The TC74VHCT138 is an advanced high speed CMOS 3-to-8 LINE
DECODER fabricated with silicon gate C2MOS technology. It achieves the
high speed operation similar to equivalent Bipolar Schottky TTL while
maintaining the CMOS low power dissipation.
When the device is enabled, 3 Binary Select inputs (A, B and C) determine
which one of the outputs (
Y0
to
Y7
) will go low.
When enable input G1 is held low or either
G2A
or
G2B
is held high,
decoding function is inhibited and all outputs go high. G1,
G2A
, and
G2B
inputs are provided to ease cascade connection and for use as an address
decoder for memory systems.
The input voltage are compatible with TTL output voltage.
This device may be used as a level converter for interfacing 3.3 V to 5 V
system.
Input protection and output circuit ensure that 0 to 5.5 V can be applied to
the input and output (Note) pins without regard to the supply voltage. These
structure prevents device destruction due to mismatched supply and
input/output voltages such as battery back up, hot board insertion, etc.
Note: VCC = 0 V

Features
 High speed: tpd = 7.6 ns (typ.) at VCC = 5 V
 Low power dissipation: ICC = 4 μA (max) at Ta = 25°C
 Compatible with TTL inputs: VIL = 0.8 V (max)
VIH = 2.0 V (min)
 Power down protection is provided on all inputs and outputs
 Balanced propagation delays: tpLH ≈ tpHL
 Pin and function compatible with the 74 series (74AC/HC/F/ALS/LS etc.) 138 type.