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TPS51200: VLDOIN pin inrush current

Masazumi Ishii
Genius 3945 points
Part Number: TPS51200
Hello.

I have a question about TPS 51200.
For details, please see the attached file.

Thank you.
2275.TPS51200.pdf
  • 0
    TI__Mastermind 24075 points
    Masazumi-san,

    In waveform 2, how much is the load current?
    In waveform 3, the load current is 0A and Cout is reduced from 30uF to 10uF, right?

    Thanks
    Qian
  • 0 in reply to Qian Chen
    Genius 3945 points

    Hello

    Thank you for your reply.

    Load current: DDR: 0.6 A

    The current of VO was measured. There is inrush current as 2A. (Attachment)

    For the capacitor of waveform 3, it is OK.

    I have an additional question.

    For details, please see the attached document.

    Thank you.

    3806.TPS51200.pdf

  • 0 in reply to Masazumi Ishii
    TI__Mastermind 24075 points

    Masazumi-san, 

    The VLDOIN current is equal to "Cout charging current" + "output current".  The Cout charging current is the current charging Cout when Vout rises up. 

    In your measurement, the VLDOIN current is 2A, output current is 0.5A, and Cout Charging current is 1.5A. 

    Thanks

    Qian

  • 0 in reply to Qian Chen
    Genius 3945 points

    Hello.

    Thank you for your answer.

    The current of VTT is measured near VO pin of TPS51200. It is between electrolytic capacitor and Vo pin.
    I think that the charging current of capacitor + load current = 0.5 A (peak). (I think this state)

    For details, please see the attached document.

    Thank you.

    TPS51200-3.pdf

  • 0 in reply to Masazumi Ishii
    TI__Mastermind 24075 points
    Masazumi-san,

    In waveform 8, VO current is oscillating.
    When the ESR of electrolytic output cap is large, the loop may not be stable and VO is oscillating. This information is available on datasheet 8.2.2.3 section page 18.

    When VO is oscillating, some power is dissipated from VO to ground. As the result, VLDOIN current is higher than VO pin current.

    During startup, TPS51200 VO current could be higher than 1A. Is it possible to use a high current module to supply 1.5V?

    Thanks
    Qian