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PGA450Q1EVM: ctune calculate

Frank Qiu
Genius 15776 points
Part Number: PGA450Q1EVM
Other Parts Discussed in Thread: PGA450-Q1, PGA460, PGA460-Q1

Hi dear expert,

In PGA450Q1EVM user guide there is a description about the tune cap Ctune "Typically, a tuning capacitor is needed to match the resonant frequency between the transducer and transformer."

i don't understand the the meaning of "match the resonant frequency", and I want to know how to derived formula about Ctune？

thanks for your help.

  • 0
    TI__Mastermind 27950 points

    Hi Frank,

    There is no accurate method of calculating the exact C_Tune value for a specific transducer and transformer pair. It is a sweeping / trial-and-error type of process.

    My strategy is to connect a capacitor bank in parallel to the transducer, and visually inspect the decay time and echo peak amplitude on the FIFO plot for each capacitor value between 100pF to 2000pF at 100pF step increments. This gives me twenty data points to compare and choose from.

    The PGA450 is an older device we are no longer encouraging customers to use, unless they need the integrated 8051 MCU. Is the customer aware of the newer PGA460 device? The PGA460-Q1 offers improved performance, lower cost, smaller package, and simplified development when compared to the PGA450-Q1. Visit the Ultrasonic E2E FAQ for a comparison of the newer ultrasonic devices: https://e2e.ti.com/support/sensors/f/1023/t/748143

    You can see more information about the matching components (tuning capacitor and damping resistor) in the PGA460 Ultrasonic Module Hardware and Software Optimization. The discussion is applicable to both the PGA450 and PGA460, and any other ultrasonic system using a transformer driver.