• TI Thinks Resolved

How to replace the damaged IC

Prodigy 20 points

Replies: 13

Views: 216

Part Number: DAC81416EVM

Hello Uttam,

Unfortunately while working on the DAC-EVM, it has got damaged by me. While working I checked the DAC IC and detected that it was heating up. After disconnecting the power supplly and other connections, I found that the VDD/VAA lines are showing a short connection. I suspect that due to a mistake in connection of the power supplies, the DAC IC has got damaged.

I wish to replace the faulty IC, and wanted to know if there are temperature sensitive components on the board and if the inner layers on the board have any temperature sensitivity.

Please guide me.

Thanks,

Sufyan Khan

  • Hi Sufyan,

    Thank you for your query. You need an experienced soldering professional to remove the QFN part and resolder a new one. This can be done without removing other components. Please refer to the following document for the correct procedure:

    http://www.ti.com/lit/an/slua271b/slua271b.pdf

    Hope that answers your question.

    Regards,

    Uttam Sahu

    Applications Engineer, Precision DAC

  • In reply to Uttam Sahu:

    Is there any other possibility other than the DAC IC being damaged for the VDD/VAA and GND line to be shorted?

  • In reply to Sufyan Khan1:

    Hi Sufyan,

    It's difficult to guess the cause of the failure without analyzing the actual environment, test conditions etc.

    I would recommend checking for all the power supply impedances before applying the power and also make sure you follow all the ABS max ratings in the datasheet even during power-up and power-down scenarios.

    Regards,

    Uttam

  • In reply to Uttam Sahu:

    Is there any way I could receive help from TI for this. I am based in New Delhi, if I can visit any TI facility in India which has people with such soldering experience, I would be willing to do so. I am a student and am not experienced with such fine soldering and fear that replacing the IC myself might result in damage to the board or other components. I have the EVM purchase details with me, if required. I know this is an unusual request but any help would be very much appreciated.

    Thanks and regards,

    Sufyan Khan

  • In reply to Sufyan Khan:

    Hi Sufyan,

    You should be able to get the soldering done from a local PCB assembly house. You should not try replacing it yourself unless you know soldering a QFN device.

    Regards,

    Uttam

  • In reply to Uttam Sahu:

    Okay thanks for the help.

    Regards,

    Sufyan Khan

  • In reply to Sufyan Khan:

    Hello Uttam,

    I was able to get the DAC IC soldered on the EVM but I am facing some issues. The hardware issue that I was facing(Short between VDD/VAA and GND line) was rectified after soldering the new IC. But now, I am not able to get output from the board.

    The SPI communication is working fine as I checked reading the Device ID and other registers that I programmed, and the values matched as given in the datasheet(Device ID) or as what I programmed(Configuration registers). But even when I am communicating with the DAC, there is no voltage at the ouput.

    Another thing I noticed is that the VIO line stays at voltage of 4.2V even when I am applying 3.3V.

    I am not able to identify the problem. If you could help me it would be very helpful.

    Thanks and regards,

    Sufyan Khan

  • In reply to Sufyan Khan:

    Hi Sufyan,

    Could you please send the following details:

    1. Jumper settings on the board

    2. Power supplies as measured at different test points

    3. Sequence of register settings

    Regards,

    Uttam

  • In reply to Uttam Sahu:

    Please find my responses below,

    1. Jumper settings on board:

    J2 = open

    J3 = open

    J9 = closed

    J10 = 1-2(selecting U2A3V3 from J7)

    J11 = 1-2(selecting VREF from REF5025)

    J12 = 1-2(selecting GND)

    2. Power supplies at test points:

    TP1 = 0.00V

    TP2 = 0.00V

    TP3 = 5.045V

    TP4 = 5.044V

    TP5 = 4.201V

    TP9 = 0.011V

    TP11 = 9.94V

    TP12 = 2.487

    TP13 = 0.00V

    3. Sequence of registers

    Register                       Value

    SPICONFIG                 0A84

    GENCONFIG               7F00

    BRDCONFIG               FFFF

    SYNCONFIG               0000

    TOGGCONFIG0          0000

    TOGGCONFIG1          0000

    DACPWDN                  0000

    DACRANGE(1-4)       0000

    TRIGGER                     0000

    BRDCAST                    0000

    OFFSET(0-3)               0000

    //INITIALIZATION COMPLETE

    //WRITING VALUE  INTO DAC REGISTER

    DAC7                            FFFF

    Even after writing into the DAC7 Register, the output does not appear on the OUT7 pin.

    Let me know if you need any more information.

  • In reply to Sufyan Khan:

    Hi Sufyan,

    Apologies for replying so late due to the holidays. Your VIO looks problematic. It should have been 3.3V but there might be another 5V source driving it. Please check that. 

    I am assuming that you are able to read/write to the DAC properly. If that's not true, please upload a scope shot of the SPI pattern to debug.

    As you resoldered the unit, you can check whether there are any shorts or dry-solder, etc. If yes, it might be a good idea to touch-up the soldering and check again.

    Regards,

    Uttam