74HC138NB データシートの表示（PDF） - Philips Electronics

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74HC138NB

3-to-8 line decoder/demultiplexer; inverting

Philips Electronics 

Philips Semiconductors

3-to-8 line decoder/demultiplexer; inverting

Product specification

74HC/HCT138

FEATURES

• Demultiplexing capability

• Multiple input enable for easy expansion

• Ideal for memory chip select decoding

• Active LOW mutually exclusive outputs

• Output capability: standard

• ICC category: MSI

GENERAL DESCRIPTION

The 74HC/HCT138 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/HCT138 decoders accept three binary

weighted address inputs (A0, A1, A2) and when enabled,

provide 8 mutually exclusive active LOW outputs (Y0 to

Y7).

The “138” features three enable inputs: two active LOW

(E1 and E2) and one active HIGH (E3). Every output will be

HIGH unless E1 and E2 are LOW and E3 is HIGH.

This multiple enable function allows easy parallel

expansion of the “138” to a 1-of-32 (5 lines to 32 lines)

decoder with just four “138” ICs and one inverter.

The ”138” can be used as an eight output demultiplexer by

using one of the active LOW enable inputs as the data

input and the remaining enable inputs as strobes. Unused

enable inputs must be permanently tied to their

appropriate active HIGH or LOW state.

The ”138” is identical to the “238” but has inverting outputs.

QUICK REFERENCE DATA

GND = 0 V; Tamb = 25 °C; tr = tf = 6 ns

SYMBOL

tPHL/ tPLH

tPHL/ tPLH

CI

CPD

PARAMETER

propagation delay

An to Yn

E3 to Yn

En to Yn

input capacitance

power dissipation capacitance per package

CONDITIONS

TYPICAL

HC

HCT

CL = 15 pF; VCC = 5 V

12

17

14

19

notes 1 and 2

3.5

3.5

67

67

Notes

1. CPD is used to determine the dynamic power dissipation (PD in µW):

PD = CPD × VCC2 × fi + ∑ (CL × VCC2 × fo) where:

fi = input frequency in MHz

fo = output frequency in MHz

∑ (CL × VCC2 × fo) = sum of outputs

CL = output load capacitance in pF

VCC = supply voltage in V

2. For HC the condition is VI = GND to VCC

For HCT the condition is VI = GND to VCC − 1.5 V

UNIT

ns

ns

pF

pF

ORDERING INFORMATION

See “74HC/HCT/HCU/HCMOS Logic Package Information”.

September 1993

2

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