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TDC1000-C2000EVM: No reponse from the COMPIN and the STOP

Hassan IDRISS
Prodigy 20 points
Part Number: TDC1000-C2000EVM
Other Parts Discussed in Thread: TUSS4470, PGA460, TDC1000

HELLO !

I'm using a tranducer 40khz, but i got nothing out of the COMPIN and STOP 

when I visualized with the oscilloscope
  • 0
    TI__Mastermind 27950 points

    Hi Hassan,

    If you are using a 40kHz transducer, I suspect you are trying to make an ultrasonic measurement through air. If this is the case, I do not recommend the TDC1000 because it is designed primarily for liquid level sensing and concentration measurements in small containers/tanks. Instead, I recommend that you consider the PGA460 or TUSS4470. You can find more information and a comparison of these two ultrasonic devices on the Ultrasonic E2E FAQ here: https://e2e.ti.com/support/sensors/f/1023/t/748143

    If you want to continue using the TDC1000:

    • To achieve a 40kHz centered driver signal, you need to use an external clock source because the divisor options for the default 8MHz clock source will not be able to achieve 40kHz. Consider using a 5.12MHz external clock source and a divisor of 128.
    • Additionally, you may need to reconfigure the external bandpass-filter passive component network between the PGA_OUT pin and the COMP_IN pins of the TDC1000. By default, the band pass network is optimized for a 100kHz to 4MHz transducer. A 40kHz signal will be heavily attenuated by the default BPF component values. You can use the TDC1000 TINA-TI Reference Design to help calculate the values required for a 40kHz centered BPF.
    • Air coupled measurement typically required a large amount of analog front end gain. You may need to increase your PGA gain to a maximum level of 21dB to see a 40kHz signal. Note the PGA460's AFE gain can be set up to 90dB, and the TUSS4470 gain is automatically configured up to 90dB also for this very reason of air coupled ultrasonics.

  • 0 in reply to Akeem Whitehead
    Prodigy 20 points

    Hi,

    Yes i'm using an external clock source and also i increased my PGA gain to a maximum level.

    What i wondering is how can i configure the external bandpass filter ? It's that i configure in the GUI or I need some modifications with the electronic circuit ?

  • 0 in reply to Hassan IDRISS
    TI__Mastermind 27950 points

    Hassa,

    The external bandpass filter must be modified as an electronic circuit. The TDC1000 device does not integrate any of the bandpass functionality, so there are no software settings for the BPF. See section "8.3.5 Receiver Filters" of the TDC1000 datasheet for details on the bandpass filter components. The aforementioned TINA circuit I linked to in my last post is a helpful tool to help you see the component impact on the bandpass filter in the frequency domain.