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TPS56628: Questions for TPS56628 Eco-mode Inductor Current Waveforms

Part Number: TPS56628
Other Parts Discussed in Thread: TPS565201

Hi Experts,

We observed the negative inductor current for TPS56628 during eco-mode, can you help to check that is this the expected behavior? Test waveform is as below:

Test conditions:

1. TPS56628 EVM.

2. VIN=12V, Vout=0.95V, R_feedback_top=15K, R_feedback_bottom=56K.

3. Load current=0.5A.

Thanks.

  • Adding more details for this issue - customer is using two open-drain circuits to adjust the TPS56628 bottom feedback resistor, schematic is as below:

    Now, this negative inductor current will be observed associated with this voltage control, but we do not know how it is occurred? Kindly help to analysis it. 

    Attached in below is the current waveform under no load condition:

    Thanks.

  • Hi Jacky,

     I did the bench test as your words.  

    TPS56628 EVM.   VIN=12V, Vout=0.95V, R_feedback_top=15K, R_feedback_bottom=56K. Load current=0.5A.Pls see the waveform shown as follows.

     Your waveform is abnormal. Pls double check.

    Gavin

  • Hi Gavin,
    Please refer to my second post which added more details about this abnormal waveform. We also did the same experiments with same conditions by using TPS565201, but didn't see such current waveforms. Not sure why TPS56628 will have such behaviors.
    Thanks.
  • Hi Jacky,

    You can send me email gavin-wang@ti.com.


    Gavin