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ADS131A04EVM: D3 is glowing RED when I connect to the USB of my computer

anand Chandrasekhar
Prodigy 220 points
Part Number: ADS131A04EVM
Other Parts Discussed in Thread: ADS131A04

I connected the ADS31A04EVM board to my computer using an USB via a 100mA USB isolator. [https://www.adafruit.com/product/2107]

When I connect without the isolator everything is working great. WHen Isolator is connected, D3 glows red !!

Can someone tell me what is going wrong ?

  • 0
    TI__Guru**** 172646 points

    Hi Anand,

    I suspect you are running into a common mode issue through the USB Isolator.  Does the same thing happen if you power the ADS131A04EVM through an external source rather than through the USB port?

  • 0 in reply to Tom Hendrick
    Prodigy 220 points
    I thought ADS131A04 EVM cannot be powered with external power supply !!

    Page 16 of : www.ti.com/.../sbau259a.pdf
    The EVM is only powered by the USB connection at J1

    I do see a slot for DC Jack. Hence I am confused !!
  • 0 in reply to anand Chandrasekhar
    TI__Guru**** 172646 points
    Hi anand,

    At the moment, I suppose we both are. I am having a hard time figuring out what D3 is supposed to represent since there is no mention of it in the Users Guide. So tell me, besides D3 glowing RED, what else do you observe with the EVM while powered through the USB Isolator? Can you verify that 'power' is actually getting to the ADS131A04EVM board? Are you able to talk to the board?
  • 0 in reply to Tom Hendrick
    TI__Guru**** 172646 points
    Hi anand,

    So it would seem that D3 is used to indicate that there is an issue with the ADS131A04EVM power generation. The DC Jack and the surrounding voltage regulators are not installed on the EVM, which is where the statement about 'USB power only' on page 16 is coming from. These are the 'DNP' components shown in Figure 12 (page 27) of the users guide. Those DNP components, ultimately provide the 'EXT_5V' shown in the lower left corner of Figure 11 (page 26). The USB isolator you have can only provide 100mA of current which I suspect is not enough to start up the ADS131A04EVM. You should be able to verify this by probing TP3, TP4 and TP5 relative to any of the GND test point. The voltage at TP3 should be 5.5 to 6V. The voltage at TP4 should be 1.8V and the voltage at TP5 should be 5V. Please measure the voltage at these test points and let us know what you find.
  • 0 in reply to Tom Hendrick
    TI__Guru**** 172646 points
    Hi anand,

    Were you able to resolve this issue?
  • 0 in reply to Tom Hendrick
    Prodigy 220 points

    Not yet. I was facing other minor issues related to ground. 

    So trying to use USB itself for powering at present just to avoid other problems.

    I will be doing the test, you had recommend, in a couple of days. I will update my findings here. 

  • 0 in reply to anand Chandrasekhar
    Prodigy 220 points
    Hello,

    Case 1:
    When connecting USB ( without Isolator), TP3 = 5.48, TP4 = 1.8v
    Case 2:
    When trying to power Board without USB, using external 6.2V power source at J5, TP3 = 0, TP4 = 0.
    I tried to switch JP3 from USB_Power to EXT_Power, Still TP3 = TP4 = 0;
    I guess, option for external Power is not installed in the Board.
    Case 3 :
    Connecting USB ( with USB Isolator ) , TP3 = 4.1, TP4 = 0;

    I guess, its the problem with USB isolator. Is it possible to use external power supply for powering the board along with USB power supply ?
    I badly want to isolate the system from ground . It seems the Ground for the USB is same as ground for the Board, without any isolation.

    Regards,
  • 0 in reply to anand Chandrasekhar
    TI__Guru**** 172646 points
    Hi anand,

    None of the power regulation components associated with J5 are installed, so using an external 6.2V supply there won't work. Those regulation components provide 5V to pins 5 and 6 of JP3. Unfortunately there is no easy test point access, but you could apply an external 5V source across C46. With that, the JP3 option should work and then your isolated USB device might be able to provide enough power to run the TIVA processor.