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TPS25830A-Q1: Schematic Review

CHO SR
Genius 3415 points
Part Number: TPS25830A-Q1

Tool/software:

Hi TI team,

Please review the customer's schematic.

TYPE-C USB charger with a 15W 1 port specification.

Schematic delete.

  • +1
    TI__Expert 4751 points

    Hi CHO,

    The schematic looks good. Here are a few suggestion:

    1.  R13 is the current sense resistor. The recommended voltage across RSNS under current limit should be approximately 50 mV as a compromise between accuracy and power dissipation. 5mOhm could be too small.

    2. Pin 9 RT/SYNC is floating in this design, is this on purpose? Generally a proper resistor is suggested here.

    3. A 10-uF cap is recommended to be placed in parallel with C28 as the C_BUS.

    4. Please consider adding pull-down resistors for DP/DN near the output connector.

    BR,

    Ke Wang

  • 0 in reply to Ke Wang
    Genius 3415 points

    Hi Ke Wang,

    Thank you for your support.

    Please review the revised schematic.

    Schematic delete.

    1.  R13 is the current sense resistor. The recommended voltage across RSNS under current limit should be approximately 50 mV as a compromise between accuracy and power dissipation. 5mOhm could be too small.

    - Instead of 15mOhm in the data sheet, we applied 10mOhm in the mass production specification. Is there any problem?

    2. Pin 9 RT/SYNC is floating in this design, is this on purpose? Generally a proper resistor is suggested here.

    -  Modified it to use 49.9kohm (400khz).

    3. A 10-uF cap is recommended to be placed in parallel with C28 as the C_BUS.

    - The VBUS on the USB TYPE-C side was moved to the appropriate C28 side.

    4. Please consider adding pull-down resistors for DP/DN near the output connector.

    -  DP, why do I apply pull-down resistance to DM?
       Usually, only damping resistance and C and L were applied, but I wonder why.

  • +1 in reply to CHO SR
    TI__Expert 4751 points

    Hi CHO,

    Thanks for your reply. Currently I don't have additional suggestions for the schematic. For your questions:

    1.  R13 is the current sense resistor. The recommended voltage across RSNS under current limit should be approximately 50 mV as a compromise between accuracy and power dissipation. 5mOhm could be too small.

    - Instead of 15mOhm in the datasheet, we applied 10mOhm in the mass production specification. Is there any problem?

          -> As long as the voltage drop across this resistor is around 50 mV it's fine. 10mOhm looks good to me.

    4. Please consider adding pull-down resistors for DP/DN near the output connector.

    -  DP, why do I apply pull-down resistance to DM?
       Usually, only damping resistance and C and L were applied, but I wonder why.

       -> The USB spec specifies 15kOhm pull-downs for DP, DN for a host/hub port, please check if you need to define the role of the board and decide if the 15kOhm resistors are required.

    BR,

    Ke Wang