HD74HC251
1 of 8 Data Selectors/Multiplexers (with 3-state outputs)
Description
This multiplexer features both true (Y)...
HD74HC251
1 of 8 Data Selectors/Multiplexers (with 3-state outputs)
Description
This multiplexer features both true (Y) and complement (W) outputs as well as a strobe input. The strobe must be at a low logic level to enable this device. When the strobe input is high, both outputs are in the high impedance state. When enabled, address information on the data select inputs determines which data input is routed to the Y and W outputs.
Features
High Speed Operation: tpd (A, B, C to Y) = 20 ns typ (C L = 50 pF) High Output Current: Fanout of 10 LSTTL Loads Wide Operating
Voltage: VCC = 2 to 6 V Low Input Current: 1 µA max Low Quiescent Supply Current: ICC (static) = 4 µA max (Ta = 25°C)
HD74HC251
Function Table
Inputs Select C X L L L L H H H H B X L L H H L L H H A X L H L H L H L H Strobe S H L L L L L L L L Outputs Y Z D0 D1 D2 D3 D4 D5 D6 D7 W Z D0 D1 D2 D3 D4 D5 D6 D7
Notes 1. H: high level, L: low level, X: irrelevant 2. Z; high impedcance (off-state) 3. D0 through D7; the level of the respective D input.
Pin Arrangement
3 2 Data inputs 1 0 Y Outputs W Strobe GND
1 2 3 4 5 6 7 8 D2 D1 D0 Y W S C D3 D4 D5 D6 D7 A B
16 VCC 15 4 14 5 Data inputs 13 6 12 7 11 A 10 B 9 C Data select
(Top view)
2
HD74HC251
Block Diagram
A B C
D0
D1
D2 Strobe
D3
VCC
D4
Y
D5 VCC D6 W D7
3
HD74HC251
DC Characteristics
Ta = 25°C Item Input
voltage Symbol VIH Ta = –40 to +85°C Max — — — 0.5 1.35 1.8 — — — — — 0.1 0.1 0.1 0.33 0.33 ±5.0 ±1.0 40 µA µA µA I OL = 4 mA I OL = ...