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Visitor lepotdenut
Visitor
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Registered: ‎10-29-2018

KC705 FMC HPC / LPC voltage

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Hello everyone,

I've been reading the user guide of the Kintex-7 FPGA KC705 Evaluation Kit.

I want to use the FMC HPC bank with bidirectionnal LVDS 1.8V. So I have to power the FMC HPC bank (VADJ_FPGA) to 1.8V.

The issue is that I also want to use the FMC LPC bank to use a mezzanine card (Ethernet FMC 1.8V). I read that there are some issues with using the Ethernet FMC 1.8V with High Range bank  (http://ethernetfmc.com/compatible-fpga-boards/). Apparently, if I use the LPC FMC with the voltage of 1.8V, I will  "not be able to use the on-board 125MHz clock oscillator unless the FPGA board has an on-board external termination resistor on this clock signal"

Is there a way to power the FMC LPC with 2.5V (so i avoid the compatibility problem with Ethernet FMC) while keeping the FMC HPC bank with a voltage of 1.8V?

Thanks for your answers,

Florian

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Community Manager
Community Manager
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Registered: ‎07-23-2015

Re: KC705 FMC HPC / LPC voltage

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@lepotdenut The HPC and LPC FMC signals are connected to HR banks on KC705. So if you need to use Bidirectional LVDS on HPC FMC pins, you will need VCCO to be 2.5V to support LVDS_25 bidirectional functionality. https://www.xilinx.com/support/answers/43989.html

When you say LVDS 1.8V, I guess that is just the operating voltage of the other end device. Do not get misled with the 1.8V as LVDS is not a rail-rail voltage. Check both the sides  Vdiff and Vcm specs are within range of each other. Take a look at this post of mine which has the pic of the LVDS signal and what Vdiff and Vcm are. 

So have 2.5V for VADJ_FPGA and you should be able to use both the cards. Also, you cannot have separate VADJ_FPGA voltage for HPC and LPC as it is a single rail and powers all the HR banks connected to FMC connectors i.e. HPC and LPC

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Community Manager
Community Manager
196 Views
Registered: ‎07-23-2015

Re: KC705 FMC HPC / LPC voltage

Jump to solution

@lepotdenut The HPC and LPC FMC signals are connected to HR banks on KC705. So if you need to use Bidirectional LVDS on HPC FMC pins, you will need VCCO to be 2.5V to support LVDS_25 bidirectional functionality. https://www.xilinx.com/support/answers/43989.html

When you say LVDS 1.8V, I guess that is just the operating voltage of the other end device. Do not get misled with the 1.8V as LVDS is not a rail-rail voltage. Check both the sides  Vdiff and Vcm specs are within range of each other. Take a look at this post of mine which has the pic of the LVDS signal and what Vdiff and Vcm are. 

So have 2.5V for VADJ_FPGA and you should be able to use both the cards. Also, you cannot have separate VADJ_FPGA voltage for HPC and LPC as it is a single rail and powers all the HR banks connected to FMC connectors i.e. HPC and LPC

--------------------------------------------------------------------------------------------------------------------
There's no such thing as a stupid question. Feel free to ask but do a quick search to make sure it ain't already answered.
Keep conversing, give Kudos and Accept Solution when you get one.
-----------------------------------------------------------------------------------------------------------------------
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