SN74LVC244A buffer spec

Aaron Spaete

Other Parts Discussed in Thread: SN74AUC244

I don’t see a maximum toggle rate called out. Should we calculate the rate from the propagation delays?

At 1.8V over -40 to +85, tpd = 10.4nS = tplh=tphl, fmax = 10.4nsx2= 20.8ns = 48mHz. (30pF load)

That would end up being a triangle/sawtooth though.

Any guidance is appreciated.

Regards,

Aaron

0 Chris Cockrill over 12 years ago

You can get approximate Fmax several ways.

easiest way is to take a clocked part in the same family pull it from that datasheet.

Most accurate way is run IBIS model into your load conditions and get rise and fall times. from this you can calculate Fmax.

Your calculations came out close. For LVC it is about 50Mhz at 1.8V

If you are running at 1.8V then you should use the SN74AUC244 instead. Fmax at 1.8V is about 300Mhz

0 Aaron Spaete over 12 years ago in reply to Chris Cockrill

Chris,

Thanks for the reply. Anything faster that the SN74LVC244 in the ZQN package? My customer is space constrained.

Or any plans to add the SN74AUC244 into a smaller package?

- Aaron

0 Chris Cockrill over 12 years ago in reply to Aaron Spaete

Have you looked at the SN74AUC245ZQNR.

The 245 is basically the same part but has a direction and 1OE pin instead of 2 OE pins.

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