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PGA460: PGA460 coefficients Bandpass

Henning Graaf
Prodigy 10 points
Part Number: PGA460 
Hello everybody,

I would like to learn more about the internal process in the PGA460.

My first question:
How are the coefficients for the bandpass filter interpreted? I looked for the possible settings via the GUI under "High-Frequency Range Bandpass Filter". 
It should also be mentioned here, that only the A2_8KHz is in the list for the A2 coefficient, but this is not important at first. 
My actual question, can I read the coefficients from these values, for example to put them in a Matlab model?

e.g. 200.4 KHz

A2_8KHZ -> DDBA -> -0.56762 (as coefficient)

B1_8KHz -> 647 -> 0.01607 (as coefficient)

So is there a special model?  The register values ​​are divided by 10,000 as above? 
Maybe you can help.
...

My 2nd question:
How long are the values ​​held in the peak hold? 

Thank you for the answer

Best regards
Henning
  • 0
    TI__Mastermind 27950 points

    Henning,

    Responding to your questions:

    1. Please see the following E2E discussion regarding the bandpass filter coefficients setting details: https://e2e.ti.com/support/sensors/f/1023/p/819254/3042619
    2. The peak-hold only applies to the output of the echo data dump for downsampling into a fixed 128 bytes of memory. If you are using the ultrasonic measurement result method of data extraction, the result is always given in 1us resolution. The peak-hold is dependent on the preset record length; calculated as PeakHoldTime = PresetRecLenTime/128 . At the shortest record length of 4.096ms, the peak-hold time is 4.096ms/128 = 32us, while at the longest record length of 65.536ms, the peak-hold time is 65.536ms/128 = 512us. As the record length increases, the echo data dump resolution decreases.