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THS1041 startup vref

Glenn Brown
Prodigy 150 points


 

I am looking at Vref on a THS1041 at startup.  Once the chip is powered up, Vref jumps to 1.08V than after ~750ms it changes to 1.00V.  Is this how it is supposed to operate normally?

 

  • 0
    TI__Expert 6040 points

    We did some test on Vref, it reaches its spec level about 1ms after power supply reach certain level, Vref is stable about 800ms late (tested). In your case, I would say it is normal because the voltage change is in the initial time (<800ms) and it is stable at 1v after 750ms. However, in your case the voltage stays at 1.08v for some time then jump to 1v looks like that there is digital activity going on in the system during the time. For example, change the state of the logic pin Mode or state of the register.

    Regards,

    Hui

  • 0 in reply to Hui-Qing Liu
    Prodigy 150 points

     

    We do write to the register, but it happens after the voltage settles to 1.00V

  • 0 in reply to Hui-Qing Liu
    Prodigy 50 points

    Hui,

     I am working with Glenn on this issue.Thank you for the feedback.

    We have been doing some additional testing. We have several of the THS1041 that either exhibit the behavior where the internal vref is at the wrong voltage for some time, and then jumps to the correct voltage, or as the case is for most units, the internal vref is continually out-of-spec. Our design uses 4 of these devices per board, and some of the devices are failing during ICT testing. The pass window is set to: 0.95>VREF>1.05 Volts.

    I ordered the THS1041 EVB, and verified that the internal vref was at 1.02V when configured for that mode (W5 in position 1-2, W7 and W9 open, W8 closed, CLAMP tied to DVDD, and Vref tied to CLAMPIN).

    I performed the following experiment:

    I transferred the THS1041 on our board that is continually at 1.10V to the eval board, and put the IC from the eval board on our board. The problem has follwed the "out-of-spec" IC to the eval baord, and out board is not within spec. The "out-of-spec IC has a lot code of 88T EXN1. The IC that was on the eval baord has a lot code of 14T AXCK.

    Also, is it possible for me to send you the schematic of our application for your review and feedback? The design is confidential and under NDA, so I cannot share it with the whole community.

    Thank you,

    Chris-

     

     

     

  • 0 in reply to Chris Crosby
    Prodigy 50 points

    Hui.

    I mis-typed a few items in the experiment that make it sound confusing. Here is what I was trying to say:

    I transferred the THS1041 on our board that is continually at 1.10V to the eval board, and put the IC from the eval board on our board. The problem has follwed the "out-of-spec" IC to the eval board, and our board is now within spec. The "out-of-spec IC has a lot code of 88T EXN1. The IC that was on the eval baord has a lot code of 14T AXCK. So, it appears that the THS1041 remains out-of spec when it is installed on the eval board in the same configuration that yielded good Vref for the THS1041 that came with the eval board. Any ideas on what might be causing this issue? This problem has been occuring on as many as 20% of the boards (where one or more THS1041 out of spec on the board). 

    Thank you, Chris-

  • 0 in reply to Chris Crosby
    TI__Expert 6040 points

    Chris,

      It sounds like you used your board to verify the failure of the EVM (20% failure). In this case, you need to contact with local TI office for the issue of the failure IC or EVM and local TI office will be able to help you.

    Regards,

    Hui