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TPSI3050: Can one capacitor be used from VDDH to VSSS.

Lauren Mayfield
Expert 7875 points
Part Number: TPSI3050

Hi team,

For both two-wire and three-wire modes, for Cdiv capacitors, can my customer just use one capacitor from VDDH to VSSS? They don’t have a switching frequency for turning On\Off the MOSFET. They will turn the MOSFET ON in the beginning of the day and turn it OFF at the end of the day. This is for a solar application.

Thanks,

Lauren

  • 0
    TI__Expert 3575 points

    Hello Lauren, 

    Thank you very much for reaching out. This could potentially work. It is not something I have tested before, but I can confirm on the bench if you could provide me more details. However, the ripple on VDDM would be a bit higher. Is there a specific reason the customer wants to use a single capacitor?

    Details needed for the test: 

    1- Input voltages for EN and VDDP

    2- CVDDP capacitor, Total gate charge or capacitance for the FET, VDDH capacitor. 

    Sincerely, 

    Francisco Lauzurique

  • 0 in reply to Francisco Lauzurique
    TI__Expert 7875 points

    Thanks for the fast reply Francisco. Let me gather this info from the customer and I'll get back to you for the bench test.

  • 0 in reply to Lauren Mayfield
    TI__Expert 7875 points

    Hi Francisco,

    Let's try this out, thank you. EN and VDDP will be 3.5V, he's going to try 3 wire config. MOSFET cap is around 10nF. He doesn't have cap values in mind for CVDDP or VDDH so if you want to select those and just let me know which ones so he can use those in his design as well, that would be great.

    He wants to use less components because he's trying to be as closely p2p compatible as he can with other devices, since they don't want to change the layout from the original design. 

  • 0 in reply to Lauren Mayfield
    TI__Expert 3575 points

    Hello Lauren, 

    Thank you very much for sharing this information. I will try this on the bench early Monday and have results for you before the end of the day. 

    Sincerely, 

    Francisco Lauzurique

  • +1 in reply to Francisco Lauzurique
    TI__Expert 3575 points

    Hello Lauren, 

    I hope you are doing well. I completed the test on the lab with CVDDP = 1.2uF, VDDP = EN = 3.5V, CDDH = 1uF, CDRV = 10nF. The waveforms show what we expected. This combination would work, however, the ripple in VDDM at lowest power transfer setting would be high. Let me know if you have any questions about the waveforms of the tests.   

    PXFR = 7.32k (Lowest Power Transfer) 

    Powerup

    EN

    PXFR = 20k (Highest Power Transfer) 

    Powerup

    EN

    Let us know if this answers all of your questions. 

    Sincerely, 

    Francisco Lauzurique 

  • 0 in reply to Francisco Lauzurique
    TI__Expert 7875 points

    Francisco, thank you so much for your help and effort here. They appreciate the testing and decided to go with two separate caps because of the ripple. 

    They plan to use this device. Thank you for helping us :)

  • 0 in reply to Lauren Mayfield
    TI__Expert 3575 points

    Hi Lauren, 

    Thank you for reaching out and feel free to reach out to us with any additional questions. 

    Sincerely

    Francisco Lauzurique