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ADS54J20: ADS54J20EVM did not work

Part Number: ADS54J20
Other Parts Discussed in Thread: LMK04828

Hi jim,

     The EVM did not work when  i changed the balun translator,and the current is small .The voltage and input after balun are normal ,could you give me some suggestion for checking?

Thanks

  • Suy,

    What did not work and what balun did you change? There is no balun on the TSW1400EVM. If this issue is about the trigger, please restore the TSW1400EVM back to its original configuration, connect a cable between J11 and J14 and use the GUI to setup for external software trigger mode. Make sure this works before trying an external trigger using your source.

    Regards,

    Jim

  • Hi jim,

        It's not TSW1400EVM but ADS54J20,my input frequency is very low so i replace the balun for ADT1-6T,but i measured the input after the balun is normal when i put into the signal。Another when i load the config file for LMK84048 and ADC the PLL locked normally,once i capture in HSDC pro there is no wave and the frequency is not correct。Did the ADS54J20 damage?

  • Suy,

    Send screen shots the HSDC Pro capture, send the config files you are using and send a picture from an oscilloscope with a differential probe connected to R2 and R5 on the ADC side of these two resistors. How much current is the ADC EVM drawing?

    Regards,

    Jim

  • Hi jim,

        Pls look my operation flow:

        1,when i power up the ADC EVM,the current is440mA

        2,after i load the config filte(LMK_Config_Onboard_983p04_MSPS.cfg),the current is about 400mA

        3,power up the TWS14J56EVM,the total current is about 1A,download the firmware the total current is 2.1A,and only the LED D3 lit on,

        4,the input signal is 50MHz 1.5V Vpp sine wave,look the the attachment of waveform(mesured by single-end probe,we have no differential probe)

        5,connect the TWS14J56EVM and capture the HSDC,i did not capture the signal,look the attachment

  • Suy,

    After you load the LMK file, you need to press the board reset then load an ADC config file.

    Regards,

    Jim

  • Yes,i did it.

    I think the current of the ADC EVM is unnormal,before this the ADC current is about 1.1A when i power up.

  • Suy,

    Make sure the current limit on your power supply is set to at least 3A for the ADC EVM. Program the LMK with the file called "LMK_Config_Onboard_245p76_MSPS.cfg. Place a differential scope probe across R32 (top side next to ADC). Verify there is a 245.76Msps clock present at these pins. This is easier to see on a scope than a 983Msps signal. If the clock is present, I think you have damaged the part. If the clock is not present, I can provide more trouble-shooting suggestions.

    Regards,

    Jim 

  • jim,

       I have measured the clk across R32 is about 247.56M,but the Vpp is only 75mv,so the lmk84048 is damage?

  • Suy,

    Check on both sides of C65 and C73 to make sure. The differential swing should be 2000mV. If you see 75mv on both sides, it would appear the LMK device is bad.

    Are you getting 122.88MHz on both sides of C91? This is the VCXO output used by the LMK.

    Regards,

    Jim 

  • jim,

      Yes,i check on both sides of c65 and c73。

       Also i check on pin4 of the VCXO the out is 122.88MHz and the Vcm & swing voltage is 1.5v,then i measured on both sides of c91,the swing voltage is about 480mv(measured by 1MΩ of osc scope)。

      Another can you tell me why did not use the differential clock to LMK04828?And the VCXO outP did not output。

  • Suy,

    The LMK can support single-ended CMOS input for a clock a source and the VCXO is a single-ended CMOS output. The board allows for either a single-ended or differential clock source to be used. The default setup provided the lowest phase noise option at the time the board was released to production.  

    Since it appears the LMK may be defective, you can either request a free sample from the TI website and swap out the device or if you bought this from a distributor, work with them to get a replacement. If you bought it from the TI Store, the following link has the details and a link to the form to start the return process.  Once you are on the returns and refunds page of the TI Store look for the hyperlink which says: TI store customer support form. 

    Regards,

    Jim

     

    www.ti.com/.../ti-store-order.html