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PGA450-Q1: PGA450-Q1: Single Ended Setup Still Has Saturation Period

Alex Bogachenko
Prodigy 30 points
Part Number: PGA450-Q1

Hello

We setup a PGA450-Q1 in a single ended configuration with 2 US sensors according to TI recommendations.

  • The changes that were made to the firmware:
    • In burst_cap_comp function the while loop waiting for the decay to be done was removed
    • In burst_cap_comp function the EN_CTRL register values were adjusted to work in a single ended configuration

  • Configuration  changes that were made to work with single ended setup:
    • BURST_MODE = 0x01
    • DEADTIME = 0x00
    • SAT_DEGLITCH = 0x00
    • BLANKING_TIMER = 0x00

After these changes when taking a measurement and we still get a saturation period as show in the picture below



And the beginning of the corresponding FIFO 

Even if the receiver sensor is fully incased in foam there is still data received as shown above.
What could be the reason for these issues? Can we get to a point where measurements can be taken stating from 1cm?

Thank you,
Alex  

  • 0
    TI__Mastermind 23045 points

    Hello Alex,

    Thanks for posting to the sensing forum! Are you using the same device connect the two transducers? In other words is the same device is generating and receive the US signal at the same time.

    If this is the case then I do not believe you will be able to achieve your 1cm measurement  without the input being saturated. Using two transducers in a bistatic format allows you to extremely reduce the blind zone caused by the ringing period in one ultrasonic transducer. But the reason that you are not able to completely eliminate the noise on the RX transducer in bistatic topology is because both transducers are connected to the same device. What occurs is due to the internal noise that is coupled to the RX stage of the circuitry when the device is trying to generate a large TX signal needed by the transducer to generate the ultrasonic pulse.

    If you want to completely eliminate the noise then it would be necessary to use separate devices, one that handles the US signal entirely and one that strictly provides the AFE to process the returned signal. This should allow you truly do the near 0 measurements, but using the same driver and receiver IC will only get you as close to 0cm as it possibly can.

    Best,

    Isaac