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ADS1274: The difference between Dout1 and Dout2

Kevin Xiong
Expert 2340 points
Part Number: ADS1274

Hi,

I'm using ADS1274 with this configuration: clk=24MHz, low power mode and SPI mode. When there is no signal on SCLK, the Dout2 has high and low level waveform, but the Dout1 does NOT change the level.

My question is: why the level status on Dout1 and Dout2 is different?

Thanks.

Kevin Xiong

  • 0
    TI__Mastermind 46360 points
    Hello Kevin,

    With SCLK idle (held low), the ADS1274 is still converting input readings as long as the master clock CLK is active. The output register is updated after each falling edge of /DRDY and the MSB of the result will be output on the DOUT pins. Since the conversion result is in 2's compliment form, the MSB will be 0 for a positive number or 1 for a negative.

    In your case, I suspect the AINx2 inputs are near 0V differential (both AINN2 and AINP2 are at the same voltage), and with noise, you are getting plus/minus reading results, which is causing the MSB to toggle.

    Regards,
    Keith N.
    Precision ADC Applications
  • 0
    TI__Guru 66246 points
    Hi Kevin,

    Thank you for your post.

    The behavior of the DOUT pins will depend on the DOUT Mode. The ADS1274 offers both a Time-Domain Multiplexed (TDM) and a Discrete Output Mode. TDM Mode uses only DOUT1 to output data from all channels. Discrete Output Mode uses a separate DOUT pin for each channel. Please refer to the DOUT MODES section in the datasheet beginning on page 31.

    Best regards,
  • 0 in reply to Ryan Andrews
    TI__Mastermind 46360 points
    Hi Kevin,

    Do you have any additional questions regarding the behavior of DOUTx?

    Regards,
    Keith