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PGA460: about CTURN” formula

Hide
Guru 21045 points
Part Number: PGA460
Other Parts Discussed in Thread: TIDA-060024, ,

Hi Team,

 

Our customer uses a formula of “Jaju747” and “slaa732a” to calculate "CTUNE ".

However, typical values for tuning capacitance ranges is different.

- Jaju747 / 2.2.5.1 Tuning Capacitor / Typical values for the tuning capacitance range from 50 pF to 5000 pF.

-slaa732a / 4.4.2 Tuning Capacitor / Typical values for tuning capacitance ranges from 100 pF to 2000 pF.

 

And, "CTURN" and "RDAMP" are different depending on the document.

Even if “TDK EPCOS B78416A2232A003" and " MURATA MA58MF14-7N" are the same combination.

- TIDA-060024 / CTUNE=0.68nF,RDAMP=10kΩ

- BOOSTXL-PGA460 EVM / CTUNE=1500pF,RDAMP=2.7kΩ

 

And, these values ​​are different from the their calculation result of “CTURN”.

They have two questions.

 

--------

[Q1]

Is there any material that explains the introduction process and theory of the formula "CTURN"?

And, which "typical values for tuning capacitance ranges" is correct(better), "Jaju747" or "slaa732a"?

 

[Q2]

Could you please let us know the measurement method (circuit) of the parasitic inductance of the transformer of “CTURN” formula?

--------

 

Regards,

Hide

  • +1
    TI__Mastermind 23045 points

    Hello Hide-san,

    Thank you for posting to the PS forum and for the question. There are two reasons that both the BOOSTXL-PGA460EVM and the PGA460PSM-EVM use different passive tuning components, the main one is due to the fact that they use a different transducer so the parasitic behavior of each of these transducers will be different and the second reason which is probably not as major as the first one is that the board layout could also have a slight impact on the parasitic components present on the board. Of course as you mentioned the different inductors could make a difference as well.

    1. Both ranges are appropriate but we typically suggest going with the 50 pF to 5000 pF range, and unfortunately we do not have any material that covers the theory for using the Ctune formula. Especially since it can be difficult for customers to obtain all the values required use the formula. Instead we recommend sweeping the capacitor values using a capacitor bank until you achieve optimal ring-decay time and amplitude of your echo. Please note that not all transducers actually require component matching.

    2. As mentioned we do not measure the parasitic inductance of the transformer for the Ctune formula and just sweep the capacitance.

    I hope this helps and please let me know if there are any additional questions!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Guru 21045 points

    Hi Isaac-san,

    Thank you for the detail information and your advice.

    Regards,

    Hide

  • 0 in reply to Hide
    TI__Mastermind 23045 points

    Hide-san glad to help out!

    Best,

    Isaac