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BQ25601: EMC Design

Wenhao Wu
Genius 9046 points

Part Number: BQ25601

Hi Team,

My customer has two questions for BQ25601 when designing it.

1. Beside inductor selection guide 9.2.2.1 in datasheet, is there any other specific selection consideration that BQ25601 requires more than a normal Buck?

2. Do we have an EMC design files for BQ25601?

Thank you for answering this question!

-Wenhao

  • 0
    TI__Mastermind 25800 points

    Hey Wenhao, 

    For 1) Please follow all of the items in section 9.2.1 Design Requirements, not only the inductor selection guide. I would also recommend following the descriptions in the Pin Functions section of the datasheet. Beyond that, we recommend all customer use the BQ25601EVM as the reference for their designs.

    For 2) We only have the EVM design files. Is this what you are looking for?

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Genius 9046 points

    Hi Joel,

    Please see my inputs below:

    (1)The customer is asking if increase inductor inductance from 2.2uH to 4.7uH, what other sepcs should take care when design?

    (2)It is  "Electromagnetic interference" not EVM. The customer is asking if we have ways to reject this from influencing other things on board.

    -Wenhao

  • 0 in reply to Wenhao Wu
    TI__Mastermind 25800 points

    Hey Wenhao,

    1) We only recommend between 1.0uH to 2.2uH on this charger. Outside of those values, the charger has not been characterized.

    As you will read in the section provided, the critical items related to the design are the output capacitor and the inductor. A larger inductor will reduce the AC current ripple, but it will also pull in the double pole frequency of the buck converter. That section has all of the design considerations we recommend.

    2) For EMI reduction, there are several things we recommend. 

    • Add 1nF capacitors from PMID and VBUS to ground to help decouple the high frequency current due to discontinuous switching.
    • Add an RC snubber footprint between SW and GND. 
    • Add a resistor between the BTST pin and the 47nF capacitor. 
    • Add a large power GND plane between the converter power plane to act as an EMI shield
    • In the worst case, customers will add a metal cage over the charging components to block radiated emissions.

    Regards,

    Joel H

  • 0 in reply to Joel Hernandez II
    TI__Genius 9046 points

    Hi Joel,

    Thanks for your reply.

    -Wenhao