1 Features
• Selects one of eight binary data inputs
• Three-state output capability
• True and complement outputs
• Typical (data to output) propagation delay of 14 ns
at VCC = 5 V, CL = 15 pF, TA = 25 ℃
• Fanout (over temperature range)
– Standard outputs : 10 LSTTL loads
– Bus driver outputs : 15 LSTTL loads
• Wide operating temperature range : – 55 ℃ to 125
℃
• Balanced propagation delay and transition times
• Significant power reduction compared to LSTTL
logic ICs
• Alternate source is Philips
• HC types
– 2 V to 6 V operation
– High noise immunity : NIL = 30 %, NIH = 30% of
VCC at VCC = 5 V
• HCT types
– 4.5 V to 5.5 V operation
– Direct LSTTL input logic compatibility, VIL = 0.8
V (Max), VIH = 2 V (Min)
– CMOS input compatibility, II ≤ 1 μA at VOL, VOH

2 Description
The ’HC251 and ’HCT251 are 8-channel digital
multiplexers with three-state outputs, fabricated with
high-speed silicongate CMOS technology. Together
with the low power consumption of standard CMOS
integrated circuits, they possess the ability to drive
10 LSTTL loads. The three-state feature makes them
ideally suited for interfacing with bus lines in a busoriented
system.