Need a faster 10-bit tri-state buffer than SN74LVC827A

John Randolph

We've got a situation in our current project where we're using the SN74LC827a to implement a mux to switch between two eight-bit BT-656 video sources, and it seems that we've painted ourselves into a corner and the parts just aren't fast enough for our needs.

As near as I can tell from the data sheets, this part was intended for 10Mhz signals, and we need to get 27Mhz data through it. Does the 29287 get us what we need?

Can someone recommend a pin-compatible replacement that will work for signals >50 Mhz? I can be reached at jcr@mac.com.

Thanks,

-jcr

over 16 years ago

0 Chris Cockrill over 16 years ago

TI__Mastermind 46480 points

Hi John

The LVC827A should run up to about 100Mhz.

Are you actually seeing problems?

0 John Randolph over 16 years ago in reply to Chris Cockrill

Prodigy 30 points

Hi, Chris.

Yes, we are having trouble with the LC827A, (oops, put the wrong part number in the heading for this thread).

Looking at the board in my hand, the topside markings on the part are:

"LC827A"

"48K"

"A8T6"

If the LVC version will handle 100Mhz, that should take care of our situation. Thanks!

-jcr

0 Chris Cockrill over 16 years ago in reply to John Randolph

TI__Mastermind 46480 points

John

The Top side mark for the LVC827A is "LC827A"

But this part should not have any problems at 27Mhz. Have you scoped the output?

0 John Randolph over 16 years ago in reply to Chris Cockrill

Prodigy 30 points

My firmware engineer has scoped the output, and the waveform he's seeing is nearly a sawtooth wave, trying to pass a 27Mhz signal through it. Looking it up on the BOM, the exact part number we specified is SN74LVC827ADBR. I'm wondering if there's a way to confirm what speed grade we actually do have on these boards, and whether a supplier may have given us the wrong parts.

What do the "48K" and "A8T6" markings mean?

-jcr

0 Chris Cockrill over 16 years ago in reply to John Randolph

TI__Mastermind 46480 points

John

I will check the markings and see if they are good. One mark is a date code and one is assembly site. Is there a way we could see the input vs the output plot and possibly this section of the schematic?

My email is c-cockrill@ti.com.

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Need a faster 10-bit tri-state buffer than SN74LVC827A