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ADS9813: With a single - ended bipolar input of ±5V, the ADS9813 has an output of 1.9V.

chaofeng chaofeng
Prodigy 30 points
Part Number: ADS9813

Tool/software:

hi：

一）The device we use is the ADS9813, and the initialization sequence for the device is as follows:

  1. Write0x0001 to register 0x00 (reset enabled).
  2. Write 0x0000to register 0x00 (reset disabled).
  3. Write 0x0004to register 0x00 (legacy SPI enabled).
  4. Write 0x000Bto register 0x04 (INIT1 configuration).
  5. Write 0x0002to register 0x03 (select bank 1).
  6. Write 0x0002to register 0x92 (INIT2 configuration).
  7. Write 0x0604to register 0xC5 (INIT3 configuration).
  8. Write 0x0100to register 0xC1 (set SDR data rate)

二）he ADC's analog input uses a single-ended bipolar ±5V signal. However, there is an issue where AINxP has a DC output of approximately 1.9V. What could be causing this problem? The schematic diagram of the analog front-end is as follows:

 

  Best regards 

  • 0
    TI__Expert 8866 points

    Hi Chaofeng,

    Thanks for your question. May I ask what kind of application/project you are using ADS9813 in?

    Please ensure you are following this init sequence. Your first few writes do not seem to match Table 6-13.

    Do you mean you are reading 1.9V output from the same pin you are applying the +/-5V input signal to? Or you are reading this output when the +/-5V input is not connected? If left floating, the inputs will show some DC value close to ~2V as this is the common-mode voltage of the internal PGA. 

    Also, a SMPL_SYNC pulse must be provided to the device after power up and initialization to ensure the channel data is aligned when output from the ADC.

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 30 points

    Hi Samiha,

    We are using it in a sound collection project.

    After the initialization sequence of ads9813 was configured according to the sequence in Table 6-3, there was still a 1.9V output. According to the content of other posts on the forum website, after changing the value of the 0x03 register in the initialization sequence to 0x0002, the output of the AINxP pin was still 1.9V.

    After power up and initialization,We  provided a SMPL_SYNC pulse to ensure that the channel data from the ADC output is aligned , but the voltage by the AINxP is still 1.9V.

    The schematic design is as follow:

  • +1 in reply to chaofeng chaofeng
    TI__Expert 8866 points

    Hi Chaofeng,

    Thanks. Are you measuring 1.9V when the inputs are floating? Because as I mentioned in my previous answer, this is expected. You may ground unused inputs. 

    Or are you measuring 1.9V when you apply your +/-5V inputs?

    Could you provide a higher resolution image of the schematic? Or a PDF? I cannot read the resistor values.

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Prodigy 30 points

    Thank you for your reply. The problem has been solved，inputs are floating