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Dedicated SERDES usage for ADC LTC2387-18 with Cyclone V?

VOS
Beginner
642 Views

Hi,

I plan to use Cyclone V with ADC LTC2387-18 (15 Msps, 18 bit).

Timing diagram of ADC’s digital interface is shown below.

 

VOS_0-1593774140733.png

 

CNV and CLK are generated from FPGA (CNV is planned to be latched externally on the board using D-trigger in order to reduce jitter), and DCO and data (DA) are sent from the ADC.

What I want is to use IP core in order to exploit dedicated resources and latch data correctly, for example SERDES – ALTLVDS_RX core. But there is an issue - DCO signal has interruptions, it doesn’t switch permanently, that means we can't use ALTLVDS_RX core as I understand, because PLL could lose lock, and lock time is very uncertain – up to 1 ms according to Cyclone V datasheet. As I understand, we can’t use ALTLVDS_RX without PLL, just clocking dedicated SERDES directly from DCO.

In that case we need to use internal FPGA resources – registers from LEs, I suppose. It is a bit strange if it is so. But maybe somebody had experience with such types of ADCs and can help me. Maybe there are ways for using SERDES with such DCO signal or another IP cores.

Thanks!

Vadim

 

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1 Solution
EngWei_O_Intel
Employee
599 Views

Hi Vadim

I hope I understand your situation correctly.

Yes, the ALTLVDS_RX is tied with a PLL. If your design has limitation towards the PLL lock time on the spec, then you have to create logics to implement the receiver.

Unfortunately we don't have sample reference design for this logic creation. For recommendation, we can make use of shift register and parallel register to construct the LVDS receiver. 

We shall always refer to "Design Guidelines" mentioned in the doc below:

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/cyc/cyc_c51009.pdf

 

Thanks.

Eng Wei

 

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5 Replies
EngWei_O_Intel
Employee
615 Views

Thanks Vadim for your inquiry. Allow me some time to go through your design question and get back to you.

 

Thanks.

Eng Wei

 

EngWei_O_Intel
Employee
600 Views

Hi Vadim

I hope I understand your situation correctly.

Yes, the ALTLVDS_RX is tied with a PLL. If your design has limitation towards the PLL lock time on the spec, then you have to create logics to implement the receiver.

Unfortunately we don't have sample reference design for this logic creation. For recommendation, we can make use of shift register and parallel register to construct the LVDS receiver. 

We shall always refer to "Design Guidelines" mentioned in the doc below:

https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/hb/cyc/cyc_c51009.pdf

 

Thanks.

Eng Wei

 

View solution in original post

IDeyn
New Contributor III
569 Views

Hi all!

 

Well, in case the PLL is tied with ALTLVDS_RX core, I suppose that maybe we could use pfdena signal for locking the DCO and so on, but in general we should create receiver logic from LEs.

 

----

Ivan

VOS
Beginner
559 Views

Hi Eng Wei!

Thank you very much for your answer.

Vadim

EngWei_O_Intel
Employee
525 Views

Hi Vadim

I’m glad that your question has been addressed, I now transition this thread to community support. If you have a new question, feel free to open a new thread to get the support from Intel experts. Otherwise, the community users will continue to help you on this thread. Thank you.

 

Eng Wei

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