broscius@grad1.cis.upenn.edu (Al Broscius) (04/09/91)
Hi Folks, Does anyone know of any TTL-compatible XOR gates that beat the 74F86 in maximum propagation delay ?? The NatSemi F series databook lists a maximum propagation delay of 7nS. Any help would be appreciated, Thanks in advance Al Broscius broscius@cis.upenn.edu broscius@dsl.cis.upenn.edu signature stuff....
roger@hpnmdla.hp.com (Roger Petersen) (04/10/91)
In sci.electronics, Al Broscius <broscius@grad1.cis.upenn.edu> writes: | Hi Folks, | | Does anyone know of any TTL-compatible XOR gates that beat the 74F86 | in maximum propagation delay ?? The NatSemi F series databook lists a maximum | propagation delay of 7nS. You could check out the 74AS86. AS is typically slightly faster than F (but you have to deal with the faster edge rates too). My latest AS databook only shows typical prop. delays, no worst case, so I don't know how fast they really are. I didn't see any XOR gates in my AC/ACT databooks. A brute-force approach would be to use a 5 ns PAL. I think you can even get a 4.5 ns PAL from AMD, since they've added a few more GND pins to the package. Roger
henry@zoo.toronto.edu (Henry Spencer) (04/11/91)
In article <7380022@hpnmdla.hp.com> roger@hpnmdla.hp.com (Roger Petersen) writes: >You could check out the 74AS86. AS is typically slightly faster >than F (but you have to deal with the faster edge rates too). >My latest AS databook only shows typical prop. delays, no worst case, >so I don't know how fast they really are. The standard rule of thumb for TTL -- although applicability to AS is a little unclear -- is that worst case over full range is twice typical. (Beware: the "max" numbers on old TTL data sheets are at 5.0000V and 25.0000degC, not over the full range.) That gives AS no advantage over F in this case. -- And the bean-counter replied, | Henry Spencer @ U of Toronto Zoology "beans are more important". | henry@zoo.toronto.edu utzoo!henry
jjohnson@cs.ucf.edu (John Jjohnson) (04/13/91)
Your best bet is to consider the BiCMOS families which several companies are now making. The chips typically use 0.8 micron CMOS for the logic and blazing bipolar i/o pads. Fast stuff: I saw a '138 decoder with a 5ns delay going up and 1ns coming down! My data books are buried real deep, but you might call some reps/distribs: Texas Instruments - I believe their series is called BCT. (74BCT86?) National Semiconductor - ? Integrated Device Technology - FCT Saratoga Semiconductor -? Performance Semiconductor -? Sorry for the lack of details. One side note: If you are by any chance using the XOR gates to create opposite phase clocks with minimum skew, there is a standard logic chip made just for that (74xx???). Its outputs are guaranteed to change with less than 1ns of skew. Someone else recently introduced a master clock "spider and divider" for distributing clocks and fractions thereof... E-mail me if you really want me to dig. Mark J jjohnson@eola.cs.ucf.edu