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DAC80502-01EVM: DAC doesn't output proper value

Shunsuke Yamamoto
Expert 8531 points
Part Number: DAC80502-01EVM
Other Parts Discussed in Thread: DAC80501, , DAC80502

Hi team,

DAC80501 on DAC80502-01EVM cannot output proper output voltage when external power supply(VDD) is used. VDD is 3.3V, and J6 is opened. For example, 0V is the output voltage of DAC80501 when the input register value is 1388.image.pngWhen J6 is shorted 1-2, DAC80501 on DAC80502-01EVM outputs proper values. My customer hasn't changed any jumper pin settings without J6 from the default jumper setting.

Could you please kindly advise me how to fix the issue?

Best regards,

Shunsuke Yamamoto

  • 0
    TI__Guru 55163 points

    Hi Yamamoto-san,

    Can the customer confirm the reference voltage? It can be measured on TP10 and TP11.

    Does the device function if they enable the reference divider (REF-DIV)? 

    Thanks,

    paul

  • 0 in reply to Paul_Frost
    TI__Expert 8531 points

    Hi Paul-san,

    Thank you for the advice! I will let my customer try your advise.

    My customer has been facing the additional issue. When my customer connected the EVM to PC via USB cable, the GUI showed the picture below.

    He tried PC restart and GUI re-install, but the GUI still shows this error. He also confirmed that VDD and VREFIO is proper values, so DAC80502/1 isn't broken.

    It is really helpful if you could give me advice to fix the issue.

    Best regards,

    Shunsuke Yamamoto

  • 0 in reply to Shunsuke Yamamoto
    TI__Expert 8531 points

    Hi Paul-san,

    I received the answers of the questions from my customer. Please kindly make comments for customer's answers below.

    Paul_Frost said:
    Can the customer confirm the reference voltage? It can be measured on TP10 and TP11.

    ->TP10-GND is 2.490V, and TP11-GND is 2.490V

    Paul_Frost said:
    Does the device function if they enable the reference divider (REF-DIV)? 

    Enabling the reference divider(REF-DIV) means changing the REF*2 from REF*1 in the GUI screen below?

    Best regards,

    Shunsuke Yamamoto

  • 0 in reply to Shunsuke Yamamoto
    TI__Genius 11850 points

    Hi Yamamoto-san,

    When you receive the "Interface Not Initialized" error, please check TP1, TP2, and TP3. This error specifically refers to the FTDI controller on the board, not the DUT. If TP1-TP3 have the correct voltage, sometimes trying to initialize 3-4 times helps it to work. If TP1-3 do not have the proper voltage, that may mean the fuse F1 has tripped. In this case, replace or short the fuse to get the FTDI working again.

    For question 2: yes, please select the "REF ÷1" button. When using VDD < 3.6V, The DAC output will not work unless this option is selected. In the register map, this is Register 4 Bit 8. This bit should be "1" when VDD < 3.6V.

    Thanks,
    Erin

  • 0 in reply to Erin Bowrie
    TI__Expert 8531 points

    Hi Erin-san,

    Thank you so much for the detailed description of how to fix customer's issue. May I know why the tripped fuse happened on customer's EVM? My customer would like to prevent it for further evaluation of the EVM.

    Best regards,

    Shunsuke Yamamoto

  • 0 in reply to Shunsuke Yamamoto
    TI__Expert 8531 points

    Hi Erin-san,

    Regarding question 2, my customer uses 3.3V output external power supply for VDD of DAC80502/1, and the DAC output is normal when the GUI setting is below.

    Based on your answer, Reference Division needs to be REF*1, not REF*2. however my customer mentioned REF*2 works, and REF*1 doesn't work. Is it okay to set REF*2 for Reference Division even when the external power supply is 3.3V?

    I cannot understand why customer's situation works..

    Best regards,

    Shunsuke Yamamoto

  • +1 in reply to Shunsuke Yamamoto
    TI__Genius 11850 points

    Hi Yamamoto-san,

    Sorry, my explanation was confusing! "REF *2" is the correct configuration for VDD = 3.3V. When I said "please select the "REF ÷1" button", I meant to click it so it turns into REF*2.

    For the fuse, sometimes this happens during the transient startup current from the DAC. You can easily circumvent this problem by powering the DAC externally, or only powering through the VDD jumper after plugging the USB in.

    Thanks,
    Erin