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LMR54410: LMR54410(F) AC model

Thomas MJ
Prodigy 10 points
Part Number: LMR54410
Other Parts Discussed in Thread: TPS560430

Tool/software:

Dear Support,
We want to simulate FRA (AC Bode plot) operation of LMR54410(F), but operating in constant current mode, with current-sense amplifier in feedback loop. Something similar to the schematic below:

(Please note that this schematic uses a similar TPS560430 and the model is only for transient simulation, not AC. The load is modeled as an LED with a dynamic resistance of 2.432 Ohms.)

Do you have an AC model available for the LMR54410(F)? Or any similar IC? We are currently using TINA, but what format the model will be in is a secondary consideration.

Our configuration with current-sense amplifier and low dynamic load resistance, drastically changes the feedback loop compared to the controller in standard CV mode. We want to perform AC analysis to select the proper components to compensate for loop stability. The transicnt analysis unfortunately takes a very long time and in no way fully answers how specific compensation components affect stability.

Thank you in advance for any help.

  • 0
    TI__Mastermind 24115 points

    Hi,

    All we have for this device and similar IC's is the transient model. There is a quick start calculator for this device and a webench model that can both provide you with stability calculations. These tools may be tricky to use however if you want to simulate the loop as a whole with the current mode-sense amplifier.

    With the transient model, you may be able to simulate load transient tests that can usually give a good marker of stability if the output voltage ripple is acceptable.

    Thank you,

    Joshua Austria

  • 0 in reply to Joshua Austria
    Prodigy 10 points

    Thank you for your reply. Unfortunately, as I wrote earlier, the transient analysis takes quite a long time and does not give us any answer about the theoretical reasons for the stability or instability of this circuit.

    As far as I can see, both Webench and the document you provided above calculate Bode characteristics for this IC in a standard CV configuration. I also found the documents www.ti.com/.../slvae09b.pdf and www.ti.com/.../slvaei7.pdf where on page 10 there is a SIMPLIS model of a similar IC and their Bode analysis. Are these models available for public? In these documents, unfortunately, we do not have explicitly given values such as RCOMP, CCOMP, CO_EA, Ri and the like.

  • 0 in reply to Thomas MJ
    TI__Mastermind 24115 points

    Hi Thomas,

    We are unable to give these SIMPLIS models here. You will need an active NDA with TI for me to support this request through your field apps engineer.

    You might have better luck if you use PSPICE instead of TINA, but SIM tools are limited regardless.

    Thank you for understanding,

    Joshua Austria