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TINA/Spice/TPS7H1101-SP: how to estimate the EST of output capacitor?

john Ma
Intellectual 280 points
Part Number: TPS7H1101-SP
Other Parts Discussed in Thread: TINA-TI

Tool/software: TINA-TI or Spice Models

TPS7H1101-SP_Load_Tran.TSC

www.ti.com/.../getliterature.tsp

Hi,

I am John Ma.

Recently, I use your TPS7H1101 in my project and have a question as below.

From above link, i got TPS7H1101 spice module. I have a question about this module.

In this module, R15 is the ESR of 220uf capacitor C10, this capacitor may be a Tantalum and we can get the ESR from its datasheet. R15 equals to 35mohm,this is reasonable.

However, for c7(100nf), it may be a ceramic capacitor. I can not find any material about the ESR of this type capacitor. Why you set R12=1mohm as the ESR for this capacitor. Do you have any experiences or any refenence?

I will appreciate for your reply, thanks a lot.

Sincerely,

John Ma.

  • 0
    Intellectual 280 points
    the title is how to estimate the ESR of output capacitor?
  • 0
    TI__Mastermind 41310 points

    John,

    In this case, I am not exactly sure why 1m and 1f were used on the ceramic capacitor. The capacitors specified are the C0805C104K3RACTU and the C0805C104K3RACTU. Neither of these have models provided by the vendor, so I am guessing that the values were used to provide the best match to the data that was measured for the performance of the board. These model values will have a much greater impact on the AC simulation (output impedance) than the transient simulation.

    If a tantalum capacitor is used, the vendor normally will provide a subcircuit model for the device (in this case, the T543X227M016ATE035 was used). This is a much more complicated model with a much different frequency response. You will notice that the transient uses a simple model, while the output impedance simulation uses the model provided by the vendor.

    If you choose to use a different ceramic capacitor, you can always use the vendor provided model (if available) or a model based off of measurements, or a simplistic model that matches the overall performance of the circuit.

    For more information on models for passives based off of measurements, please take a look here:

    Steve is considered to be the best authority on this topic. He has published several papers and guides for how to get accurate models from measurements. 

  • 0 in reply to Britt Brooks - Online Design Tools
    Intellectual 280 points

    Thank you very much for your reply,sir.