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Original question:

BQ25710: VDDA capacitor rating

BQ25710: Minimum DC rating at REGN

Kazuto Tatsumi
Intellectual 2820 points
Part Number: BQ25710

Hello team,

My customer want to know the minimum DC voltage rating of the capacitor at REGN. It's recommended 2.2uF or 3.3uF in the datasheet, is that effective capacitance or not? How much is the minimum DC rating?

Regards,
Kazuto

  • 0
    TI__Genius 11385 points

    Hi Kazuto-san,

    The REGN cap will be exposed to the voltage of the REGN LDO, which is 6V. However, it is recommended to select a capacitor with a higher voltage rating for safety margins.

    The 2.2 uF and 3.3 uF on the datasheet is the rated value of the capacitors. User will need to decide what type of capacitor they can afford and use given their application.

    Your customer can refer to the EVM. The EVM uses a 0603, 35V,  2.2 uF cap on REGN. The datasheet of the capacitor is available on the manufacturer website for reference.

    Thanks and I hope this helps,

    Peng

    *If my answer solves your question, please press "This Resolved My Issue" on the thread.  

  • 0 in reply to Pengzhao Zhu
    TI__Intellectual 2820 points

    Hi Peng,

    Thanks for your suggestion. To select the capacitance for minimum value, is my understanding below correct?

    "The REGN capacitor on the EVM GRM188R6YA225KA12D has 0.88uF at 6V, so that the capacitor has 1uF@6V should be selected considering some margin."

    Regards,
    Kazuto

  • +1 in reply to Kazuto Tatsumi
    TI__Genius 11385 points

    Hi Kazuto-san,

    The primary function of the REGN pin is to provide the gate drive for the MOSFETs and the capacitor is there to help provide that instantaneous current demand to drive the gate. If the selected MOSFETs have too large of a gate charge, more current will be needed from the cap to help charge the gate.

    1uF@6V is a derated capacitance value that works for the operating conditions and MOSFETs on the EVM. In generally, I would say 1uF@6V derated is the minimum they need to have on the REGN cap. However, as their operating conditions (such as MOSFET selection) may be different from the EVM, it is recommended to have some margin on both the derated capacitance and the voltage rating.

    Thanks and I hope this helps,

    Peng

    *If my answer solves your question, please press "This Resolved My Issue" on the thread.  

  • 0 in reply to Pengzhao Zhu
    TI__Intellectual 2820 points

    Hi Peng, thanks for your description. I understood the purpose of REGN cap.