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THS1206: Same output value on both the differential channels of THS1206

Prakash B B
Prodigy 140 points
Part Number: THS1206

Hi,

I am working on THS1206 ADC interfaced to FPGA (XC7A75TFGG676-2L). The 2 control registers programmed as: CNTR0 = 0x0C8 and CNTR1 = 0x410. When I am reading the data from the ADC for both the channels data out is same. The 2 inputs are connected as: AINP-AINM with differential sine wave with 3 kHz of 1.2 Vpp and BINP-BINM are shorted i.e., 0V. I tried keeping both these differential inputs open then also both outputs are appearing same.

I am adding screenshot for your reference which the case when channel A is differential input and channel B is shorted. The CONV_CLK is 6 MHz. DATA_AV is togging but it's not periodic. Would you let me know why am I getting same output value for both differential channels? Why DATA_AV doesn't toggle periodically?

Thanks

  • 0
    TI__Guru**** 172646 points

    Hi Prakash,

    Assuming you followed the flow chart of Figure 34 (you need the 0x401, 0x400 sequence), your values for the control registers looks fine.  Curious to know what _adc_curr and_adc_nxt are in your screen capture.  From the _data_out - it would appear that nothing at all is changing much.  If you have a full-scale sine on AINx, I would expect to see values between 0x800 and 0x7FF.  As the THS1206 is a pipeline converter, you need to wait before doing the initial read.  Please review Figure 26 and note the DATA_AV and td(Pipe) signals. If you violate the td(Pipe) delay, it will have an impact on how the DATA_AV output reacts.  It looks periodic to me in the screen capture you sent, so is if changing on a wider time scale than what you have shown?

  • 0 in reply to Tom Hendrick
    Prodigy 140 points

    Hi Tom,

    Thanks for the response.

    Since I am using state transitions, those signals are meant for current and next states.

    I am taking care of the flow chart of Figure 34 as well as initial read also. In the captured screenshot the DAT_AV signal looks to be periodic since it's zoomed one. But it is not periodic for wide range of period.

    I am still not getting why both the channels output is same? Am I missing anything?

    Regards

  • 0 in reply to Prakash B B
    TI__Guru**** 172646 points

    Can you share your schematic?