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CCS/PGA970: Heating issue

Anuj Sharma40
Intellectual 360 points
Part Number: PGA970

Tool/software: Code Composer Studio

I have just assembled 4nos of  PGA970 SoC on my PCB with all 4 connected on same SPI lines to a microcontroller. I have not downloaded the firmware onto these chips but just on powering the board the 5V supply dips and the SoCs are heating up and drawing 1.6amps. Kindly advise what could be the issue. Thanks

  • 0
    TI__Mastermind 31655 points
    Hello Anuj,

    Was the PCB tested and operating normally before this? What kind of debug have you done so far?

    Is the board clamping the current output of your power supply, or is this just the maximum amount that is being drawn?

    Can you please post your schematic?

    Regards,
  • 0
    Intellectual 360 points
    Dear Scott,
      As required pl find attached the schematic for your reference. This board is being designed and  tested first time  using PGA970.



    Thanks, 

    With Best Regards,

    Anuj Sharma

    Lead Scientist 
    Mobile- +91 8149002994
    Anusandhan Technologies, 
    F-107, Ashoka Plaza, Viman Nagar 
    Pune, Maharashtra, India 
    Landline no.:7028119793



  • 0 in reply to Anuj Sharma40
    Intellectual 360 points
    Dear Scott,
      As required I have posted the schematic and am awaiting your response. Today I tried same again on another board but have got same results/overheating issue. Pl note that we are not using the external MOSFET for regulation and Gate pin is connected to ground as mentioned in the PGA970 datasheet. I am now trying to program the firmware using XDS-110 debugger. Kindly let me know what is it that we are doing wrong/incorrect. The current of 1.6Amps, it seems is clamped by the LM7805 regulator though there is no physical short found in Vcc and ground. It seems that  there occurs a short circuit within the SoC the moment it receives power of 5VDC. Kindly take this as urgent and reply.
    Thanks
    Anuj
  • 0 in reply to Anuj Sharma40
    TI__Mastermind 31655 points

    Hi Anuj,

    From your schematic it looks like you have AVDD and DVDD tied to your voltage input VCC. The AVDD and DVDD pins are outputs of internal regulators. Your problem is most likely related to AVDD (3V) and DVDD (1.8V) trying to regulate back to their intended voltages.

    Please see the PGA970EVM for a basic reference of how to connect these pins:

  • 0 in reply to Scott Cummins
    Intellectual 360 points

    Dear Scott,

       Thanks for pointing out the error which seems to be a major one too. Also could you pl let me know the values of C18 and other such capacitors that are marked DNP?

    Also as a feedback, it would be nice to add a complete  reference design in the PGA970 datasheet so that new users like us do not commit such mistakes. As one has to struggle quite a while to understand design and component values. Anyways thanks for your help as it has definitely hit the nail on the head.