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TPS659039-Q1: SMPS45 Vout issue

Neal Zhu
Expert 2470 points
Part Number: TPS659039-Q1

Hi

After power on, the smps45 voltage changes from 1.06v to 1.175v (the load does not change). The measured voltage waveform is shown in the figure below. What is the reason? The datasheet is 1.06v.

Thanks！

  • 0
    TI__Genius 13216 points

    Hi,

    Thanks for the question. In order to further clarify your problem I'd like to get some additional information from you.

    How many boards is this happening on?

    Is this happening at every startup?

    Can you verify that input voltage and input and output capacitance are all within the limits listed in the datasheet?

    Thanks,

    Daniel W

  • 0 in reply to Daniel W
    Expert 2470 points

    Hi

    Every board，

    Yes， happening at every startup，

    Yes，Reference EVM design.

    Thanks！

  • 0 in reply to Neal Zhu
    TI__Genius 13216 points

    Hi Neal,

    Thank you for the information. The supply voltage from SMPS45 may be changed over I2C during operation. If the processor is requesting the voltage change as described in this note on Adaptive Voltage Scaling it should not be a problem to operation. You should be able to check this by monitoring or temporarily disconnecting I2C communication between the pmic and the processor.

    Thanks,

    Daniel W