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Webench/TPS54540-Q1: Webbench Load Transient Simulation Fails after running Re-Comp tool

Julio Apps
Expert 3665 points
Part Number: TPS54540-Q1
Other Parts Discussed in Thread: TPS54360, TINA-TI

Tool/software: Webench

Hi,

I am having issues running a load transient simulation after adjusting the compensation on the TPS54540-Q1 device using webbench. After running the Re-Comp tool and applying the changes to the circuit ,which only updates the values on the COMP pin, i am unable to run load transient simulations but all other simulations run just fine. What can i check to get this working again? or can it be a limitation of the tool?

Thank you,

Julio Sanchez

Fail Message:

Your simulation failed due to a convergence problem in the simulation netlist. If you recently changed a component in the BOM or changed a simulation related parameter, try changing it back to its previous value. If the problem persists, it may be due to an internal problem in our system. The problem has been logged and the development team has been notified. If you have any questions, please submit a feedback online at webench.ti.com/.../.

Error File Contents:
Simulation: FAIL
* ERROR * Transient analysis failed due to convergence problems. The transient parameter cmin=<value> could be helpful; it smooths abrupt transitions by adding the given capacitance to ground for every node. (SOLVER-12)
* ERROR * Transient analysis failed due to convergence problems. The transient parameter cmin=<value> could be helpful; it smooths abrupt transitions by adding the given capacitance to ground for every node. (SOLVER-12)
**************** ERROR/WARNING COUNT ****************
ERROR: Signals not found...pun2xxx conversion not done.Exit
* WARNING * TNOM is not defined on diode model main_block.d1.wb_diode. (DEVICE-23)
* WARNING * TNOM is not defined on diode model main_block.u1.wb_tps54360.d_d1. (DEVICE-23)
* WARNING * Device x_main_block.x_u1.r_r1 is shorted to 0 and will be removed. (EXPANDER-28)
* WARNING * Device x_main_block.x_u1.rpwrpd_0 is shorted to 0 and will be removed. (EXPANDER-28)
* WARNING * Device x_main_block.x_u1.rpwrpd_1 is shorted to 0 and will be removed. (EXPANDER-28)
* WARNING * TNOM is not defined on diode model main_block.u1.wb_tps54360.d_d.main_block.u1.wb_tps54360.dd. (DEVICE-23)
* WARNING * RS is not defined or equal to zero on diode model main_block.u1.wb_tps54360.d_d.main_block.u1.wb_tps54360.dd (DIODE-2)
* WARNING * Resistor x_input_block.x_vin.rsource has zero value. (RESISTOR-20)
* WARNING * Following dangling devices will be removed: x_main_block.x_u1.v_v47 (TOPOLOGY-50)
* WARNING * Following net will be removed after pruning dangling devices: x_main_block.x_u1.set0 (TOPOLOGY-51)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * Required transient step is limited by TMIN(1e-15) at time 270402 ns. (TRAN-20)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
* WARNING * Required transient step is limited by TMIN(1e-15) at time 270402 ns. (TRAN-20)
* WARNING * TIspice could not achieve requested tolerance at 270402 ns. (SOLVER-7)
**************** ERROR/WARNING COUNT ****************
Type: DEVICE #errors: 0 #warnings: 3
Type: DIODE #errors: 0 #warnings: 1
Type: EXPANDER #errors: 0 #warnings: 3
Type: RESISTOR #errors: 0 #warnings: 1
Type: SOLVER #errors: 2 #warnings: 7
Type: TOPOLOGY #errors: 0 #warnings: 2
Type: TRAN #errors: 0 #warnings: 2
--TOTAL-- #errors: 2 #warnings: 19

FAILED SIMULATION
Status = Fail

  • 0
    TI__Intellectual 2405 points

    Hi Julio,

    As I can see from the error message you attached, the design is giving Convergence Issues due to tolerance limits set on WEBENCH (particularly CMIN parameter). One thing I can recommend is, you export the design to tool of your preference e.g. PSPICE or TINA-TI and try simulating it there. It may not necessarily be the issue with design, just parameter tolerance limits which are causing the convergence issue. Usually WEBENCH constraints are more stringent for simulations.

    As I don't have your design specifications for which re-comp has been applied, I am not able to replicate the issue at my end. Kindly use the share design option to forward the design to us if you can not resolve the issue with above mentioned steps.

    Thanks!!

    Best Regards,

  • 0 in reply to Mahavir Jain
    TI__Expert 3665 points

    Hi Mahavir,

    Thank you for the suggestions. I restarted webbench and the simulation ran just fine. I would still like to understand the convergence issue, it is not very clear to me. You mention parameter tolerance limits. Could you elaborate a bit more on this, im not sure what that is referring to. Is this parameter tolerance of the chosen components?

    Webbench Design: https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=785F4C2B1F36B6E5

    Thank you,

    Julio

  • 0 in reply to Julio Apps
    TI__Intellectual 2405 points
    Hi Julio,

    The WEBENCH simulations in background run on TISPICE as circuit simulator environment. It is similar to other circuit simulators like PSPICE and TINA-TI. All three tools try to mathematically calculate next time step response of different nodes in circuit, based on certain equations that represent the physical world components e.g. R = V/I for simple resistor. These voltage and currents are calculated within acceptable error limits called tolerances or alternatively Analysis Parameters. These are different from components tolerances you mentioned.

    You can go to TINA-TI >> Analysis >> Set Analysis Parameters to see list of such parameters for a particular simulation in TINA-TI. Sometime it's speed vs accuracy trade-off in simulations. Sometimes the tool is not able to calculate the next correct solution with number of iterations etc.

    We try to tweak these Analysis parameters to resolve convergence issues if convergence is caused due to simulator tool and design is assumed to be accurate.

    I hope this clarifies your doubt. For more details you ca refer TINA-TI >> Help >> Contents >> Analysis Menu>> Set Parameters documentation.

    Thanks!!

    Best Regards,
  • 0 in reply to Mahavir Jain
    TI__Expert 3665 points
    Thank you Mahavir, this is very helpful.

    Best,

    Julio