TPS548D21: Startup, steady_state and Bode plot

Tony Wang

Part Number: TPS548D21

1. In the PSPICE files provided with TPS548D21, there are two designs, Startup and Steady State, could you tell me what the difference are between two models used in two designs?

2. Could you tell me how to run Bode plot with the models provided?

Thanks,

over 5 years ago

0 JohnTucker over 5 years ago

TI__Guru**** 191445 points

Tony,

The start up design starts out from the state at t=-0. There are no voltages applied at that time. The Vin is stepped up and the circuit is turned on and the output voltage ramps up according to the soft start time.

The steady state design calculates the circuit from the steady state conditions, bypassing the start up.

The TPS548D21 model is a transient time domain model. You cannot use it for frequency domain analysis such as Bode plots.

0 Tony Wang over 5 years ago in reply to JohnTucker

Intellectual 310 points

Hi John,

Thanks, two more questions for you.

1. with transient time domain model, can I run AC sweep analysis or frequency domain analysis?

2. where can I found the frequency domain model for Bode plot or other frequency domain analysis?

Thanks again,

Tony

0 JohnTucker over 5 years ago in reply to Tony Wang

TI__Guru**** 191445 points

Tony,

You can only do time domain simulations with the transient model. So far as I know there aren't any modeling tools for AC analysis. I can check with a colleague about it though.

0 Tony Wang over 5 years ago in reply to JohnTucker

Intellectual 310 points

Thanks,

Tony

0 Kit Nguyen over 5 years ago in reply to Tony Wang

TI__Intellectual 2460 points

Hi Tony,
1. Please let us confirm with simulation team on this. At the mean time, you can try to run the AC analysis on that file.
2. We have the encrypted Simplis to run the bode plot. Are you Ti employee? If yes, please send me an email. You can look up my name (Huy(Kit) Nguyen) in the system. If you are not Ti employee, I need to ask upper management before we can send out the model.
Also, you can run the bode plot on the EVM too. I wrote this blog of bode plot measurement for this family.
e2e.ti.com/.../comparing-bode-plots-in-d-cap3-control-mode

0 Tony Wang over 5 years ago in reply to Kit Nguyen

Intellectual 310 points

Thanks, I am not a TI employee. I work for Microsemi/Microchip.

0 Kit Nguyen over 5 years ago in reply to Tony Wang

TI__Intellectual 2460 points

Hi Tony,
Do you have any Ti FAEs or sale team to assist you?
Kit

0 Tony Wang over 5 years ago in reply to Kit Nguyen

Intellectual 310 points

yes, John Louie is the FAE supports us.

0 Kit Nguyen over 5 years ago in reply to Tony Wang

TI__Intellectual 2460 points

Hi Tony,
Let's me contact John so that we can support you better.
Kit

0 Tony Wang over 5 years ago in reply to Kit Nguyen

Intellectual 310 points

Hi Kit,
I tried with steady state model for AC sweep analysis, but it does not work, I can't see curves.
Thanks,
Tony

0 JohnTucker over 5 years ago in reply to Tony Wang

TI__Guru**** 191445 points

Tony,

The transient model was never meant for frequency analysis. You can look at the load step response to check for over/critical/uderdamped response or for oscillations that would indicate instability.

0 Kit Nguyen over 5 years ago in reply to Tony Wang

TI__Intellectual 2460 points

Hi Tony,
I sent the encrypted Simplis model to John. It can do both AC and Transient. Let's me know if you need further help. YOu can also ask John to add you/me to the email chain or my email so that you can contact me directly.
Kit

0 Tony Wang over 5 years ago in reply to Kit Nguyen

Intellectual 310 points

Thanks Kit

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TPS548D21: Startup, steady_state and Bode plot