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FPGA - ADC & DAC for TDR

Riccardo Cecchi
Prodigy 40 points
Other Parts Discussed in Thread: AFE7225, ADS5403, DAC3174

Hi,
I need to implement a TDR (Time Domain Reflectometer) for cable fault detection. My system should inject a very narrow pulse (rise time less than 5 ns) into a RG# cable terminated with an open and samples it at high speed to measure the reflected wave. The acquired data can be used to estimate some cable parameters and to detect faults.

My sistem shall provide:
* High speed ADC > 0.3 Gsps
* High speed DAC > 0.3 Gsps
* Countinuous acquisition for at least 10 us @ 1Gsps (which is enough to test a 900 m cable with 60% velocity factor)
* Pulse injected into the cable shall be 5-10 Vpp, depending on cable length
* Raw data shall be buffered during acquisition and sent to a host PC once acquisiton is completed, or streamed while acquiring (if possible)
* Possible interfaces between host PC and TDR: USB, RJ45. If possible, avoid using PCI
* Implementation: I/O interface and in-stream data processing must be implementend using an FPGA. This is the most important requirement.
 
I would appreciate some advices about the most suitable TI products you would use for this design. I saw TI provides many boards for all its ADCs and DACs. Have you got any board with both ADC and DAC? Or a FPGA based kits capables of interfacing with two boards, one for the DAC and one for the ADC?

I'm also wondering if it would be better to buy one of the FPGA evaluation kits provided by Xilinx, such as the ML605 which also has two on-board FMC connectors. What solution does TI provide for those boards and how can I use them to implement TDR?

Any advice will be appreciated.

Thanks,
Riccardo Cecchi

  • 0
    TI__Mastermind 18095 points

    Riccardo:

    There are several options.  The AFE7225 includes dual DAC and dual ADC at 250/125 MSPS respectively.  If you need more speed then you can operate with discrete DAC and ADC device.  There are a variety of options that you can search for on TI.com.  One option on the ADC is the ADS5403 operating at 12 bit, 500 MSPS.  One DAC option is the DAC3174 also operating at 500 MSPS (14-bit).  These parts have EVMs that can interface with our pattern/capture tool: TSW1400.  This is an FPGA platform with appropriate software that can generate patterns for the DAC and capture patterns from the ADC.  In order to utilize DAC/ADC simultaneously you would need a TSW1400 for each device.  It is possible to connect these EVMs to existing FPGA development kit and TI does provide some adapter boards to facilitate the connection; however, you would need to develop the FW to generate and capture the patterns.

    --RJH 

  • 0 in reply to RJ Hopper
    Prodigy 40 points

    Thank you RJ,

    I'm planning to buy a ML605 board by Xilinx, which has two FMC connector (LPC and HPC). I saw TI provides FMC-DAC and FMC-ADC adapters compatible with AFE7225EVM. Is this a feasible setup

    AFE7225EVM + FMC-ADC & FMC-DAC adapters + ML605

    and what else do I need to implement my TDR (e.g. clock generator)?

    Again, thank you.

    r.c.

  • 0 in reply to Riccardo Cecchi
    TI__Mastermind 18095 points

    RC:

    Yes, the adapter cards are a feasible set-up.  That is their purpose.  The AFE7225 provides a clocking solution on the board so you are good to go in that department.

    --RJH

  • 0 in reply to RJ Hopper
    Prodigy 40 points

    Thank you again, RJ

    But I still have some concerns. Looking at the adapters, it's seems to me they can't be both plugged to my board, for a simple mechanical reason: the ADC-FMC seems too short... Are you sure one can plug them to the ML605 at the same time?

    Moreover, Xilinx ML605 has two FMC connector, but only one is HPC: the one I should plug to the FMC-DAC adapter supports LPC only. Would this cause any problems?

    Thks

  • 0 in reply to Riccardo Cecchi
    TI__Genius 12965 points

    Riccardo,

    Please check into the TSW4200 for an example - this was something that was done to demonstrate the capability of using a separate DAC and an ADC with the ML605.  Avnet also had some tutorial using the ML605 with the adapters and the TSW4200 - this was referred to as the Speedway Demonstration Tutorial - you will need to contact Avnet for this.

    http://community.em.avnet.com/t5/Virtex-6-DSP-Development-Kit/Speedway-Demonstration-Kit/td-p/4806

    http://www.ti.com/lit/ug/slwu071c/slwu071c.pdf

    http://www.ti.com/lit/ml/slab058/slab058.pdf

    There are enough LVDS pins on the HPC and LPC for these adapters to work for ADC and DAC EVMs.

    For the AFE7225EVM which has both ADC port and DAC port on the same EVM, it can only be plugged into either the FMC-ADC or FMC-DAC adapter boards, not both at the same time.  The adapters were meant for a separate ADC and DAC connection.  If you want to plug in both sides of the AFE7225EVM there are some HSMC or FMC flexible extender/adapter cables that can be used to make this connection.

    Ken.

  • 0 in reply to Ken C
    Prodigy 40 points

    Thank you Ken,

    TSW4200 apears to be what I'm looking for, although Avnet marked it as unavailable...