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BQ25731: BQ25731 layout query

Part Number: BQ25731


I want to design with BQ25731. The input current is very small, and need the chip in the OTG output state and in Boost mode.

We hope to achieve the highest efficiency in the OTG output state.

For the above condition I want to know whether the RAC can place to C position or not.

Waiting for your reply.



  • Hi Star,

    Thanks for reaching out. In boost mode, Q1, Q2, RAC, and the output caps form the output high di/dt loop so it is best to minimize the enclosed area for maximum performance (lowest EMI).

    To answer your question, yes, it is actually preferred to put RAC close to the capacitors. The closer the components in that section, the less resistive lost the circuit will have. However, depending on the power level, I would recommend having enough spacing between them to assist with thermal performance.

    Some guidelines on the BQ25731 layout is on page 87 of the datasheet: 

    Hope this helps,


  • Hi Peng

    Thanks for your reply.

    I would like to know whether it is possible to exchange the position of the RAC resistor B with the position of capacitor C?
    Then the output of Q1 first passes through the output capacitor and then to RAC.



  • Hi Star,

    I would not recommend doing it. From both current sense and efficiency standpoints, even if there are benefits, I think it would be negligible. 

    The EVM is a tested design so I would recommend following it. In general, the more integrated an IC is, the more you want to reference the EVM. Please reference the EVM.



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