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Altera_Forum
Honored Contributor I
1,231 Views

LVDS output High Z or both to '0'

Hi, 

I have LVDS output.  

Is there a any way to put both LVDS outputs to High-'Z' or either both driving '0' ?  

 

-Tero
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5 Replies
Altera_Forum
Honored Contributor I
70 Views

To my knowledge, no. If you have an output set in LVDS mode it always operates as a differential pair.

Altera_Forum
Honored Contributor I
70 Views

 

--- Quote Start ---  

Hi, 

I have LVDS output.  

Is there a any way to put both LVDS outputs to High-'Z' or either both driving '0' ?  

 

-Tero 

--- Quote End ---  

 

 

Yes, you can disable (tri-state) LVDS outputs. You should be able to infer this in your HDL code or you could instantiate an Altera I/O buffer primitive (ALTIOBUF I think). You will need an output enable signal to enable/disable the output buffer. But as Galfonz said, you can't make an LVDS output buffer drive both sides low.
Altera_Forum
Honored Contributor I
70 Views

Tristateable Bus LVDS drivers are always emulated LVDS. There should be no basic problem (besides some timing drawbacks) to connect it trough logic gates. 

 

--- Quote Start ---  

Bus LVDS (BLVDS) output uses two single-ended outputs with the second output programmed as inverted. 

--- Quote End ---  

Altera_Forum
Honored Contributor I
70 Views

Thanks, FvM, I didn't know that. To the OP, sorry for the misinformation (I was going from memory - always a mistake). 

 

If you are able to add external components I've used M-LVDS transceivers from TI. Analog Devices also makes them I believe. They also provide some protection if the LVDS signals are going off-board.
Altera_Forum
Honored Contributor I
70 Views

That should work, but you won't be able to operate as fast as real hardware differential drivers (if that matters to you).

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