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TPS548B22: problems on POP and AC analysis under SIMPLIS simulation

Kaihang Zhou
Prodigy 40 points
Part Number: TPS548B22

Tool/software:

Hi,

I got problems when I simulate the TPS548B22 under SIMPLIS. The pop analysis always fails when I want to simulate the closed loop characteristics. Pls help me with the simulation model. https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/234/TPS548B22_5F00_TRANS_5F00_Steady_5F00_State.sxsch

  • 0
    TI__Guru 56865 points

      

    You will need to run the transient analysis first, this will establish the DC operating point for the simulation.

    After you have run the transient analysis, you can run the  POP and AC Analysis.

    It is unfortunate that Simplis doesn't execute the simulation in that order.

  • 0 in reply to Peter James Miller
    TI__Prodigy 40 points

    Hi Peter,

    I've checked the simulation order which is AC analysis after transient analysis, but the error still occurs. I suspect there exist inadequate simulation parameters in it. Would you mind help me check the simulation model. I would appreciate it if you can help!

  • 0 in reply to Kaihang Zhou
    TI__Guru 56865 points

      

    I made some adjustments to get it to converge.  I am working through the adjustments I made to see what the minimum number of changes are to get it to work.

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/234/TPS548B22_5F00_TRANS_5F00_Steady_5F00_State_5F00_adjusted.sxsch

  • 0 in reply to Peter James Miller
    TI__Prodigy 40 points

    Thanks a lot. I success in the AC analysis and could you pls tell me where you adjust the simulation model to prevent me from having the same problem in the future.

  • +1 in reply to Kaihang Zhou
    TI__Guru 56865 points

      

    The adjustments I had to make to get the AC Analysis to run:

    1) Update the POP Trigger element to use a threshold voltage of 2.5V and the "divide by 2" option

    2) Update the Pop Analysis settings for a 5μs maximum period (needs to be longer than 2 switching cycles due to the divide by 2 on the POP trigger)

    3) In the Advanced Pop Settings increase the Convergence threshold from 1p to 500n and check "Use snapshot from previous transient analysis" 

    That should allow you to run the POP and AC analysis on the schematic.

    https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/234/TPS548B22_5F00_TRANS_5F00_Steady_5F00_State_5F00_w_5F00_POP.sxsch

    While working on the schematic, I noticed that the output voltage isn't actually set for 5V, it's set for 4.836V

    Vref = 1.2V, Rtop = 10kΩ, Rbot = 3.3kΩ 

    1.2V × (1 + 10kΩ / 3.3kΩ) = 4.83636V

    If you change the bottom resistor value to 3.16kΩ (Standard E48 value) you can get the output voltage close to 5V.

    If you need to stick to E24 resistor values, Change R15 to 2.0kΩ and change R23 from 165kΩ to 75kΩ to change the reference voltage from 1.2V to 1.0V.

  • 0 in reply to Peter James Miller
    TI__Prodigy 40 points

    Thank you very much for your enthusiastic help!

  • 0 in reply to Kaihang Zhou
    TI__Guru 56865 points

    Happy to help.  I am going to close this thread.  If you have any additional questions, please as a new question.