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Altera_Forum
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14 years ago

5v TTL to/from LVTTL

I need to work with ancient 5v TTL digital components built on 74xx series chips and would like to know, how to covert LVTTL voltage from Stratix II to 5v TTL and back? Any good known way to do th...
Altera_Forum's avatar
Altera_Forum
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14 years ago

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All signals are unidirectional.

I need to connect 5v TTL to 3.3 LVTTL FPGA and not to burn FPGA input driver accidentally :)

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How many bits?

Pericom 8-bit PI74LPT245, 16-bit PI74LPT16245 are bidir, 244s will be unidirectional.

http://www.pericom.com/pdf/datasheets/pi74lpt16244.pdf

TI, Fairchild and others have parts too. Eg., Fairchild

http://www.fairchildsemi.com/ds/74/74vhc244.pdf

Type in '244' into their parts browsers ... actually, type it into Digikey.

The key thing to look for in the data sheet is to check that the inputs are 5V tolerant when the device is powered from 3.3V. The part numbers will be things like LPT for the Pericom, LVC I think for TI, etc.

Cheers,

Dave