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TPS548B28: Questions about the calculation tool

Part Number: TPS548B28

Hi team, 

  

I downloaded the calculator for TPS548B28. I found it missed a sheet named partData when I used it. So, some formulas can’t work. Could you help to share the correct one?

(F43 F44)

Thanks.

Best regards.

Aylin

  • Click enable  on the yellow bar.

    Go to cell E42 and select an option 

    Go to InputSheet  click cell F1 and then click "Pull Values from Calculator Sheet"

    Click Save. 

  • Hi David,

         Thanks very much for your reply. I still have a question:

    I can’t understand the remote sense description in the datasheet very well. Could you help to share an example of remote sense connection and check if the connection in my design is correct?

        

    The attachment is our design. We will change R13,R20 to 100ohm for remote sense. Please help to check if we need any more change.

    Thanks.

    Best regards.

    Aylin12v_0p85v_10p6a_tps548b28_1.pdf

  •   Figure 8-1 on page 26 shows the simplest remote connection  https://www.ti.com/lit/ds/symlink/tps548b28.pdf#page=26.

    The customer schematic is set up for several configurations.     The local and remote terms in the schematic is different than datasheet.   the remote in datasheet is refering to the use of VSNS-.      The schematic is always using VSNS- but will sense the output near the load (remote) or local near Cout

    When R8 and R11 are installed R20 and R13 will not be.

    When R20 and R13 are installed R8 and R11 will not be. 

    C12 will be used when R8 and R11 are used and will not be used R20 and R13 are used.   DCAP3 needs output ripple to have stable operation, C12 helps overcome noise pickup or low ripple.

        I am not sure of the purpose of C29.  

    R8  R11 R20 R13 C12 R2 R1 R3 R50 C4 C29 R12
    Remote KP Remote KN Local P Local N Local C HS fb resistor LS fb resistor LS fb resistor FF resistor Feedforward Cap 0.01uF 10 ohm testing frequency response
    Yes Yes Not Installed when R8, R11 used Not Installed when R8, R11 used AC couples ripple to aid stability yes yes yes Yes yes   yes
                           
    Not Installed when R20, R13 used Not Installed when R20, R13 used Yes Yes should NOT be needed/installed when connectiing locally yes yes yes Yes yes   yes
  • Hi David,

         Thanks very much for your reply.

    In customer's design, they connected remote sense to the on-die sense of CPU and at the same time they kept the local sense which has 100ohm sense resistor (R13 and R20) to avoid the convertor out of regulate when CPU is not installed. For C29, I think it is bypass capacitor.

    Please help to check if it is okay. 

    Thanks again.

    Best regards,

    Aylin

  • Yes, the 100 ohm resistors are okay.  It is sometimes referred to as a "fail safe" connection for an open cpu socket.    

    C29 is small value and should be alright.  C29 may have a slight influence on the loop, becuase the R12 and C29 form a RC filter. 

  • Hi David,

         Thanks very much for your reply. Do we have any other suggestions about the C29?

    Best regards,

    Aylin

  • I never see a C29 between the bode resistor and  the feedback resistors on  a schematic.   I am inclined to remove it. 

    Test with and without C29 and judge based on the results.