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TPS546D24: Can TPS546D24 work with TPS546B24 in parallel operation?

Alan Chang
Intellectual 2320 points
Part Number: TPS546D24
Other Parts Discussed in Thread: TPS546B25, , , TPS546B24A, TPS546A24A

HI,

  I'd like to confirm if TPS546D24 + TPS546B25 can work in parallel operation for much output current (40A + 20A = 60A). 

  I got this mixed circuit from end customer ref. circuit. 

  • 0
    TI__Expert 8100 points

    Hi Alan,

    My colleague will give you reply next week!

    BRs

    Zixu

  • 0
    TI__Guru 56965 points

     

    There is no TPS546B24, but the TPS546D24A and TPS546B24A can be used in parallel in the form of a 2-phase stack to support 60A of load current.

    The TPS546B24A will current share to 1/2 of the current of the TPS546D24A, so the B24A will carry 1/3 of the load current and the D24A will carry 2/3.  NOTE:  The TPS546A24A does not work in a stack like this with the TPS546B24A.

    A couple of notes:

    1) The TPS546D24A should be configured as the stack controller with GOSNS connected to GND and VOSNS connected to the output.

    2) The TPS546B24A should be configured as the follower with GOSNS pulled up to BP1V5.

    3) The inductor for the TPS546B24A should be 2x the inductor value for the TPS546D24A.  If their inductor values are not 2:1, compensation must be designed so that the same ILOOP gain can be applied to both converters.

    4) The Current Limit (IOUT_OC_FAULT_LIMIT) selection for the follower (B24A) should be at least 1/2 that of the controller (D24A).  If programming IOUT_OC_FAULT_LIMIT or IOUT_OC_WARN_LIMIT via PMBus, the value written to the PMBus should either be:  N x Desired Phase Current Limit for the D24A, where N is the number of phases.  This will be this will be 1 1/3 the desired current limit for a 2-phase consisting of a D24A and B24A.

    5) If using the TPS546X24A excel design tool you can use a 3-phase TPS546B24A design for the design spreadsheet.  Select an inductor value that is the lower of the inductor value used for the B24A or 2x the value for the D24A, but make sure to use a 2-phase design for correct pin-programming of MSEL2.