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WEBENCH® Tools/TPS54424: Auto Compensation

patrick nefos
Expert 1850 points
Part Number: TPS54424
Other Parts Discussed in Thread: TPS54320, TPS54623

Tool/software: WEBENCH® Design Tools

Hello,

I am trying TPS54424 in Web Bench for a design that has 5V,3.3V,1.8V and 1V rails. The high efficiency due to low rds on of the fets will help my sealed box design thermally.

1V@2A simulated well, but 5V@1A will not auto-compensate even with default BOM components.

It does sim and numbers look reasonable @ 200Khz. I though maybe the custom 18+u inductor is the reason, so I tried a 15u, with same results, Error: Unable to compensate, relax specification limits and try again.

What Limits? I have use TPS54320 for same rail (not as efficient) and 5V@1A works fine and compensates.

Patrick

  • 0
    TI__Mastermind 35165 points

    Hi Patrick,

    We should be able to get this work and the issue is likely caused by the component selection routine we have in WEBENCH for this part. What input voltage did you input? I'll see if I can figure out where it is going.

    I was able to get a reasonable design using 12 V input, 5 V @ 1 A then changing the fsw to 200 kHz. The link below should send you to the design I made.

    https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=2D415FC8271F2137

    Best Regards,

    Anthony

  • 0 in reply to Anthony F
    Expert 1850 points
    My input is 9-15V. Auto-Compensate gives same error in file you sent me as well, so maybe a tool thing? - Patrick
  • 0 in reply to patrick nefos
    TI__Mastermind 35165 points
    Oh, I think I misinterpreted the issue. The auto compensate on the re-comp tab is not working because the default minimum Low Frequency Gain is set at 60 dB. The low frequency gain however is 51.62 dB and it is not possible to re-compensate this design to meet the minimum of 60 dB. If you change the Min to 40 dB instead, the auto compensate works.
  • 0 in reply to Anthony F
    Expert 1850 points

    TPS54424

    Anthony Fagnani said:
    Oh, I think I misinterpreted the issue. The auto compensate on the re-comp tab is not working because the default minimum Low Frequency Gain is set at 60 dB. The low frequency gain however is 51.62 dB and it is not possible to re-compensate this design to meet the minimum of 60 dB. If you change the Min to 40 dB instead, the auto compensate works.

    Anthony,
    In my simulations for load transient the TPS54424 has a much lower dip than overshoot. The Xilinx 1V core needs to be fairly controlled (+/-5% or better) +/-3%
    is my target. Do you have a suggestion for this?
    Patrick
  • 0 in reply to patrick nefos
    TI__Mastermind 35165 points

    Hi Patrick,

    Can you send me the schematic you are currently simulating and do you have a preferred switching frequency? With this I can help suggest some component values to try. You may need to decrease the L, increase the C or tune the compensation.

    Anthony

  • 0 in reply to Anthony F
    Expert 1850 points
    Hi Anthony,

    I am designing for 5V, 3.3V, 1.8V and 1V high efficiency 200KHz (sealed box) Ultrasound based on (2) solutions attached 1.8V Sims in both parts. In both cases transient load sim needs improved.

    My process, set basic design in web bench, 2A 9V-15V 2A, change inductor and caps, auto compensate and simulate. Bode looks better on TPS54414 (no red)

    TPS54424 webench.ti.com/.../SD2.cgi
    TPS54623 webench.ti.com/.../SD2.cgi

    Patrick