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Electronics Forum / Basics / April 20068:1 Multiplexer IC that's faster than 74HC151?
Hi, I am after an 8:1 multiplexer IC (in fact I have 6 inputs to route to 1 output) and the 74HC151 would be ideal, except its propogation delay is too long (33ns over -40 to 85degC) in this particular case. The inputs are TTL but outputs of 3.3V would be fine, so I hoped there would be an equivalent part in the LCX family for faster propogation (20ns max is what we need). However, the 74xx151 seems only available in HC and HCT. Is there another 8:1 multiplexer IC available, or can another logic IC (e.g. a quad 2-input multiplexer) be connected in such a way to form an 8:1 multiplexer? I 've noticed a lot more quade 2-input multiplexers available and they are also found in LCX family, unlike the 74xx151. Many thanks, -- Jim >Hi, > [quoted text clipped - 9 lines] >multiplexer? I 've noticed a lot more quade 2-input multiplexers available >and they are also found in LCX family, unlike the 74xx151. --- http://www.fairchildsemi.com/ds/74%2F74F151A.pdf  SignatureJohn Fields Professional Circuit Designer >>Hi, >> [quoted text clipped - 5 lines] >>part in the LCX family for faster propogation (20ns max is what we need). >>However, the 74xx151 seems only available in HC and HCT. <snip> > http://www.fairchildsemi.com/ds/74%2F74F151A.pdf Very many thanks, John. That's perfect. -- Jim > Hi, > [quoted text clipped - 14 lines] > -- > Jim Jim, Philips had the 74Fxx series wich were much faster than 74LSxx, even faster than 74Sxx. If memory serves power consumption was generaly between these ones. The switching characteristics of some of them was somewhat special. I remember the "first incident wave" characteristic which required some passive components when you tried to control high impedant (in casu CMOS) components with them. In one case I could not get rid of the reflections even with short wires (traces). Nevertheless a 74F151 - if available - may be a good choice. Another option is programming the devices yourself using GALs or similar programmable devices. They also look like a litle bit old fashioned these days but GAL22V10 are still available and come with propagation delays below 10ns. petrus bitbyter |
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