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AFE5809EVM: Decimation w/o demodulation and external trigger

Jonathan Geronga
Expert 7930 points

Part Number: AFE5809EVM
Other Parts Discussed in Thread: AFE5809, AFE5808,

Hi Team,

I'm posting on behalf of our customer in their question regarding TIDU702:
tidu702.pdf

1. What exactly is required to decimate for a signal starved sonar acquisition? Note: for my application demodulation is NOT desired, but decimation is desired.
- in TIDU702, p 23 indicates that an external trigger is required to trigger the DEMOD block in the AFE5809. But my signals are so low frequency that I demodulation is unnecessary. And Fig 21 seems to indicate that demod can be bypassed.
- is it necessary to test using an external clock, or can we use the eval board’s internal clock to get started?
- what firmware is required to decimate without demodulation?
- “Frame clock error in Read DDR to file” message appears when trying to use AFE5809_16x firmware. I cannot find AFE5808_09_16b firmware in the dropdown
- I can acquire triggered data using AFE5809_14x firmware, although phase appears to be shifted

2. Vref – can we reduce it for signal starved applications?

3. gain validation - please confirm that for AFE5809, 14 bits acquisition, 1 count ~ 2^{-14} V (I compute gain assuming 2^{-14} V/count and do not always realize 54 dB gain when LNA and PGA gains are set to 24 dB and 30 dB, respectively)

Please let me know your inputs.

Thanks,

Jonathan

  • 0
    TI__Expert 6040 points

    Jonathan,

    Thanks for looking at the AFE5809 device! 

    please refer to the user manual of the AFE5809EVM, Fig. 10 shows the required setup when  you use the demodulation block. either demodulation is enabled or byapssed. 

    Synchronized clock , signal and trig are reuqired in this setup. 

    you should be able to find the AFE5809_16x file under 

    C:\Program Files (x86)\Texas Instruments\High Speed Data Converter Pro\1400 Details\ADC files\AFE5809_16X.ini

    you can't adjust the VREF, which is fixed internnally . our ADC is 2Vpp input range. so the resolution is about 2Vpp/16k in the 14bit mode.   hope it will help you match to the gain calculation. 

    Thanks!