74HCT237D 查看數據表（PDF） - Philips Electronics

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74HCT237D

3-to-8 line decoder / demultiplexer with address latches

Philips Electronics 

Philips Semiconductors

3-to-8 line decoder/demultiplexer with

address latches

Product specification

74HC/HCT237

FEATURES

• Combines 3-to-8 decoder with 3-bit latch

• Multiple input enable for easy expansion or independent

controls

• Active HIGH mutually exclusive outputs

• Output capability: standard

• ICC category: MSI

GENERAL DESCRIPTION

The 74HC/HCT237 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/HCT237 are 3-to-8 line decoder/demultiplexers

with latches at the three address inputs (An). The “237”

essentially combines the 3-to-8 decoder function with a

3-bit storage latch. When the latch is enabled (LE = LOW),

the “237” acts as a 3-to-8 active LOW decoder. When the

latch enable (LE) goes from LOW-to-HIGH, the last data

present at the inputs before this transition, is stored in the

latches. Further address changes are ignored as long as

LE remains HIGH.

The output enable input (E1 and E2) controls the state of

the outputs independent of the address inputs or latch

operation. All outputs are HIGH unless E1 is LOW and E2

is HIGH.

The “237” is ideally suited for implementing

non-overlapping decoders in 3-state systems and strobed

(stored address) applications in bus oriented systems.

QUICK REFERENCE DATA

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

SYMBOL PARAMETER

CONDITIONS

tPHL / tPLH

CI

CPD

propagation delay

An to Yn

LE to Yn

E1 to Yn

E2 to Yn

input capacitance

power dissipation capacitance per package

CL = 15 pF; VCC = 5 V

notes 1 and 2

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

TYPICAL

HC HCT

UNIT

16

19

ns

19

21

ns

14

17

ns

14

17

ns

3.5 3.5 pF

60

63

pF

ORDERING INFORMATION

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

December 1990

2

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