Importance of buffering

Discussion to talk about hardware related topics only.
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DBrunermer
Posts: 67
Joined: Thu Apr 21, 2011 7:06 am
Location: Pittsburgh, PA

Importance of buffering

Post by DBrunermer »

Hello all, <MOD5272>
I'm designing a mixed voltage board where all but one of the components is a 5V device. I'm going to use a '164245 dual supply buffer for the 5V side of the board, but I was wondering, do I absolutely have to buffer the data bus for the other component? I know on my Dev-Kit 1.12 board they do, but in my final design I won't be using the dev board, and the data bus will just go to a CPLD on the 3.3V side, and just the buffer on the other side. Should that be OK, or do I really have to buffer everything? Note, I will never try to read from the bus, just write to it.
Thanks,
Dan B.
rnixon
Posts: 833
Joined: Thu Apr 24, 2008 3:59 pm

Re: Importance of buffering

Post by rnixon »

If you are only connecting to one device, and that device is very close to the processor, you are "probably" ok, meaning there is still some risk but it is low. A bigger issue may be your cpld driving the databus on power-up when it is not initialized. Buffers are cheap, I would go the safe route since it eliminates the problem.
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