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Original question:

LM5164-Q1: Strange SW waveforms

LM5164-Q1: SW and BST pins do not rise to Vin and Vin+5V respectively during SW on.

Jacob Herbold
Prodigy 10 points
Part Number: LM5164-Q1

Tool/software:

This problem is extremely urgent for my company. We are unable to build or product because the buck regulator circuit is not functional.

I have this circuit which worked in a pervious version of the design. The core of the design is unchanged but the buck regulator is not working properly.

The key symptom is the SW and BST not rising high enough during high-side switch on. The scope capture below is typical.

CH1: SW pin

CH2: Vin pin

CH3: BST pin

CH4: Vout, 3V3

  • 0
    TI__Guru 58691 points

    Hello Jacob 

    Please use a differential probe and measure the voltage difference between VIN and SW. Sometimes the probe DC offset causes the issue. Also, It will be helpful if you can share more waveforms (both zoom-in and zoom-out). 

    I will be out of office and I will not be able to reply this E2E post anymore.
    If you are still trying to resolve the issue, please don't reply on this post, but create a NEW post to get a help from other engineers quickly.
    -EL