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TPS53681: TPS53681+CSD95410/CSD95480 PWM abnormal issue

William Wu
Prodigy 80 points
Part Number: TPS53681

Tool/software:

Dear Sir,

We have found that the TPS53681, whether paired with the CSD95410 or the CSD95480, exhibits inconsistent timing in the PWM signals.

As shown in the image below, you can see that whether we use the TPS53681 with the CSD95480 or the CSD95410, there's inconsistent timing of the PWM pulses. 
This phenomenon occurs randomly on Phase A or B of our product, and even on both phases. Could you please help us confirm whether this behavior is normal?
Normal Situation
Abnormal (TPS53681+CSD95480)
Abnormal (TPS53681+CSD95410)
  • 0
    Prodigy 80 points

    revised the above description, the normal situation should be like below

  • 0 in reply to William Wu
    TI__Expert 4345 points

    Hi,

    Is this behavior seen during a transient or under static load?

    Could you also share the controller configuration (.xml) file for me to review?

    Regards,

    Troy

  • 0 in reply to Troy Johnson
    Prodigy 80 points

    This voltage conversion is only provided for use by our SoC. I'm not sure about the internal state of my SoC, but this state can be reproduced when idle.
    also attached the xml for your reference,
    BTW, des this XML configuration have an option to adjust the PWM so that it doesn't change dynamically?
    TPS53681_CSD95480 0.0 Address 97 Project File.xml

  • 0 in reply to William Wu
    TI__Expert 4345 points

    Hi,

    The controller changes the PWM timings in order to respond to load transients. The configuration parameters can be adjusted to increase or reduce the speed/strength of this response, but it cannot be completely disabled.

    If a transient is occurring, changes in the PWM timings are normal. Some jitter, or minor inconsistencies in the PWM timings, may occur at static load depending on how the controller's configuration is set.

    if you want to remove the PWM timing inconsistencies you showed, then changing the controller tuning parameters to slow the response can help. Could you try increasing the RAMP value, currently set to 200mVp-p, to 240 or 280?

    When configuring the device with TI's Fusion Digital Power Designer, RAMP is found under the Transients tab. 

    Please let me know if this change has the desired impact on the PWM timings.

    Regards,

    Troy