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ADAU1467_AD1938 hardware design?

Category: Hardware
Product Number: ADAU1467

In my project, The chip is ADAU1467 and AD1938, AD1938 matched with some hardware circuit to realize DA and AD function.  the detailed circuit shows in the figure. There are some capacity to filter the DC signal, so that the DC signal can not been feed into the ADC. Can you give me some suggestions?  my purpose is that the DC signal generated by arbitrary waveform generator can been read by DSP and show in the readback function. I am looking forware your reply. Thank you.

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  • Hello yangkun1,

    Sorry for the delay in response.

    I think you can try with AUXADCs. 

    If the DC signal is just a constant, then you can use a GPIO which only gives you two states. i.e. a HIGH or a LOW.

    If the DC signal is varying its state (different voltage level) then you can go with AUXADC.

    The AUXADCs output a 10-bit value. So, this value ranges between 0 and 1023. It can be read by the readback cell.

    For example, you can refer the below AUXADC (used as a potentiometer) circuit from the ADAU1467 eval board.

    Here the voltage varies between 0V and 3V3. The voltage 0V produces an integer 0 and a voltage 3V3 produces an integer 1023. So, you can choose based on that.

    Below is the necessary info on the voltage level to be aware of.

    I guess your app is that a DC generator will generate a random voltage level (within the range) and eventually the DSP uses that 10-bit integer number for any operation. To verify the number, it must be read by the DSP. Is that right?

    If you need anything else, then please tell us a little more info about your application.

    Regards,

    Harish

  • The auxADCs (10-bits)resolution is not enough for our application,In my application, I want to read the temperature information by means of the resistor of Pt1000, and the temperature measurement circuit is current source driving. The 10-bits ADC can not recongnise the tempeature resolution at 0.001℃. can you give me some advices. than you for your repl\y.

  • Hello yangkun1,

    I think this application will require either an ADC that is a current input or a current to voltage converter amplifier that feeds a higher resolution ADC. The AD1938 is a Sigma-Delta type of converter which is not the best for a signal that is close to DC or slowly moving DC. the full 24 bits of resolution will not be possible. It will probably be closer to 16 bits. The other issue is drift. The internal common mode reference will have some drift over time and temperature. If this is used for data where accuracy is very important then you might want to use an external voltage reference and shut off the internal reference. 

    That all said, you might want to talk to our data converter group to see what they have to say. They are the experts in data conversion where audio is my specialty. 

    (+) Data Converters - EngineerZone (analog.com)

    What is always tricky is interfacing the data converters to the DSP serial input ports. We use slightly different standards and language for the serial data but it should be possible to interface the ADC to the DSP. 

    Dave T

  • Thank you for your reply. You mean that I should add another ADC like PCM1804 in my project,  and the ADC interface with my DSP board by serial port, can you give me some example about this? or I should ask the data group for answer?