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Original question:

LM5160A: Sporadically blow up of IC; Short circuit

LM5160A: LM5160A VCC failure

WOO JEONG HUN
Prodigy 10 points
Part Number: LM5160A

Tool/software:

I would like to inquire about the defect while using LM5160A.

The circuit diagram is as follows and the output waveform of the defective B/D is as follows.

If 10V is forced from the outside after deleting diode D517 for this defect, the IC will operate normally again.

Therefore, it is assumed that the internal VCC regulator is defective.

Can you explain the mechanism of the defect??

  • +1
    TI__Expert 6422 points

    Hi Woo,

    Try reducing Rboot (R666) around 10 Ohms to 50 ohms and connecting a 1uF high-quality X7R ceramic capacitors at VCC pin (as recommended in datasheet) and check if the issue is resolved. What is the operating Vin?

    Regards

    Arpita

  • 0 in reply to ARPITA NATH
    Prodigy 10 points

    Hello Arpita

    Thanks for your answer

    Vin voltage is 37V. However, the Vin voltage is not applied. but the defect occurs.

    Can the defect occur depending on the boot resistance and the capacity of the VCC pin MLCC? I don't understand.

  • 0 in reply to WOO JEONG HUN
    TI__Expert 6422 points

    Hi Woo

    At what input voltage you captured the waveforms of VCC, where VCC is shown to be 2.99V? The VCC regulator is internally current limited to 30 mA (minimum). So, any load exceeding those limits will affect VCC. It is recommended to follow datasheet values of C_Vcc for stable and reliable operation of the IC. 

    Regards

    Arpita

  • 0 in reply to ARPITA NATH
    Prodigy 10 points

    Hellow Arpita

    There is no input voltage in the waveform shown.
    It is a waveforme of the IC output of the defective board.

    Yes, the VCC voltage is 2.99V. That's why I think the internal VCC Regulator failed.

    Does it mean that the current in the VCC may be over 30mA if the MLCC lacks capacity??

    Regards

  • +1 in reply to WOO JEONG HUN
    TI__Expert 6422 points

    Hi Woo,

    What was your applied input voltage when you observed VCC=2.99V? Can you please try reducing Rboot (R666) around 10 Ohms to 50 ohms and connecting a 1uF high-quality X7R ceramic capacitors at VCC pin (as recommended in datasheet) and check if the issue is resolved.