WEBENCH® Tools/TPS65311-Q1: Input impedance of the Buck converter

Hello Jagadeesh,

I have not worked with our models for this device, I have notified the device owner in case he is able to help.

In the meantime, have you read any of the documents regarding use of the PSPICE models? For example, I was able to quickly find this one: www.ti.com/.../sloa070.pdf

Hello Jagadeesh,

Could you please let me know the more background for your request? i,e what you are trying to achieve/solve with this input impedance simulation for a switching regulator?

These models are behavioral transient simulation models for switching regulators and AC analysis cannot be done with it. TI does not provide S parameter models for switching regulators.

Regards,

Murthy

Hi Murthy,

Thanks for the reply. Well I have an input filter before the Converter. I just want to ensure that the middlebrook criterion is satisfied. As in, the output impedance of the input filter should be way less than the input impedance of the converter. Is there any other possibility that i could simulate this??

Thank you.

Hello Jagadeesh,

Thanks. We don't have any model to do such analysis. Are you trying to design the input filter for EMC purpose?

So far, I am not aware of any issues we faced with switching regulator stability due to input LC filter. Of course, with high-Q LC filter, you may have issues with damping, but this can be addressed with different damping methods.

For the input filter design itself you can refer to the below application note:

www.ti.com/.../snva489c.pdf

Regards,

Murthy

Hello Murthy,

Thank you. I understand that, to your knowledge there has not been any issues with the stability of the switching regulator. But, still I would like to simulate and know the possible values of the input impedance over some frequency range. Is there any document that describes the control loops of the component, so that i can roughly estimate or design a similar model to simulate? It would be really grateful.

Thank you once again..