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TPS63802: Inductor and output capacitor value larger than recommend value

Satoshi
Guru 19485 points
Part Number: TPS63802

Datasheet is described L and Cout recommend value, attached below. 

Can L and Cout value exceed recommend range, no problem? (For example, L: 2.2μH~ and Cout: 200μF~) 

【Background】

・I simulating TPS63802 with Vin: 3.3V~4.5V, Vout: 5V, Iout: 1.8A, FPWM, on Webench tool.  

　But, when simulating Load transient and Input transient, peak current became large and reach current limit(4A_min, 5A_typ).

・I trying to adjustment good peak current.

　When increase L and Cout value became a little decrease peak current, but transient voltage getting worse.

・I guess that datasheet recommend value is the condition of stable with TPS63802's internal compensation specification. (is it correct?)

　If my guess is not correct, I will consider to change L and Cout value much larger than recommend value for decrease peak current.

If there the other idea for good transient specification, please let me know together.

Best regards,

Satoshi

  • 0
    TI__Expert 4760 points

    Hi Satoshi,

    The LC value can increase according to your design. Usually, the system will still be stable when the value are larger. But when you choose larger value, the size will be bigger. There should be a trade off.

    Another way to improve transient specification is to add feedforward capacitor. The application note below could be a good reference.

    Best Regards,

    Yichen Xu

  • 0
    TI__Expert 4760 points

    Hi Satoshi,

    Is there any update?

    Best regards,

    Yichen

  • 0 in reply to Yichen Xu
    Guru 19485 points

    Hi Yichen

    Thank you for advice,

    I found happy medium for L: 2.2uH and Cout: 47uF ×4, and I confirming to customer about OK or NG the L and Cout value.

    Please wait a few days for customer's answer.

    I addition, Webench data occur large inrush on startup and feel low phase margin, I already suggest to customer about application note for external feed forward capacitor (you attached) and soft start circuit. 

    ※Webench data is attached.

    TPS63802simulation.pdf

    Best regards,

    Satoshi