74HCT238PW 查看數據表（PDF） - Philips Electronics
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74HCT238PW Datasheet PDF : 7 Pages
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Philips Semiconductors
3-to-8 line decoder/demultiplexer
Product specification
74HC/HCT238
FEATURES
• Demultiplexing capability
• Multiple input enable for easy expansion
• Ideal for memory chip select decoding
• Active HIGH mutually exclusive outputs
• Output capability: standard
• ICC category: MSI
GENERAL DESCRIPTION
The 74HC/HCT238 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/HCT238 decoders accept three binary
weighted address inputs (A0, A1, A2) and when enabled,
provide 8 mutually exclusive active HIGH outputs
(Y0 to Y7).
The “238” features three enable inputs: two active LOW
(E1 and E2) and one active HIGH (E3). Every output will be
LOW unless E1 and E2 are LOW and E3 is HIGH.
This multiple enable function allows easy parallel
expansion of the “238” to a 1-of-32 (5 lines to 32 lines)
decoder with just four “238” ICs and one inverter.
The “238” 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 “238” is identical to the “138” but has non-inverting
outputs.
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
E3 to Yn
En 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
14
18
16
20
17
21
3.5
3.5
72
76
UNIT
ns
ns
ns
pF
pF
ORDERING INFORMATION
See “74HC/HCT/HCU/HCMOS Logic Package Information”.
December 1990
2
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