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  • TI Thinks Resolved

DAC8760: Output Error

Intellectual 480 points

Replies: 6

Views: 50

Part Number: DAC8760

We are writing through spi via arduino to DAC Input pins but not able to write anything on that and Output pins are also showing 24V continusly 

Design File is attached. 

[07] - Digital Output.zip

  • Hi,

    I think the design file attached does not have DAC8760. Please share the schematics.

    Regards,

    AK

  • In reply to Dheeraj yadav:

    Hi,

    I am not seeing any issues with the schematics you shared. Whats the power supply sequencing? AVDD comes up first and then +3V3_AO ?

    Also since you are using internal DVDD generated supply to power the isolator and DAC, did you verify you are getting DVDD after power up?

    Where are you measuring the output voltage, header 2, P5 in schematics? 

    Can you verify the connections between Vout and Vsense pin is there? Why I am asking to this to verify is the fact that you are getting 24V as output shows the output buffer is rail out.

    Last but not least, share the SPI frame, CS/, SDI, and SCLK on the DAC side, not on the isolator side.

    Regards,

    AK

  • In reply to Akhilesh K:

    Yes, AVDD comes first and then +3V3_AO also we are getting DVDD after power-up.

    We are measuring the output voltage at P6, P5 is for current output.

    Yes, the connection between Vout and Vsense is there. 

    We are interface Arduino SPI to our DAC and written 5V on it using the following code - 

    /*
      DAC8760 DAC Example
      CLR   - connected to GND
      LATCH - D10
      DIN   - D11/MOSI
      SDO   - D12/MISO
      SCLK  - D13/CLK
     */
    #include <SPI.h>
    #include <digitalWriteFast.h>
    #include <DAC8760.h>
    DAC8760 dac;
    void setup()
    {
      //init Serial port
      Serial.begin(9600); 
      while(!Serial); //wait for serial port to connect - needed for Leonardo only
      //init DAC
      Serial.println("Init DAC...");
      dac.begin();
      dac.write(0); //0 32767 65535
    }
    void loop()
    {
      //do nothing
    }

    Library used can be found on this link - https://github.com/watterott/Arduino-Libs/tree/master/DAC8760

    After writing the DAC value we tested the voltage on several points on board - At P6, Pin 21 but the value is fluctuating sometimes to 5 V to 1V and then it decreased to 0.5v to 1v itself. 

     

  • In reply to Dheeraj yadav:

    Hi,

    Thanks for checking all the recommendations.

    Please do  share the SPI frame, CS/, SDI, and SCLK on the DAC side, not on the isolator side.

    Regards,

    AK

  • In reply to Akhilesh K:

    Hi,

    In your schematics, AVSS is not grounded to GND_ISO_AO.

    Please connect the same and test it.

    Regards

    AK

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