AD5360 is always busy

Hi. I am working with a DAC IC called AD5360 (datasheet:http://www.analog.com/media/en/technical-documentation/data-sheets/AD5360_5361.pdf)

it has a 24 bit SPI interface and it supposed to work like this: !Busy is always high and when you send data to DAC, !Busy goes low for brief amount of time and then again it goes high.

the problem is the !Busy signal is always low. I checked connections multiple times but everything seems right but it doesn't work. when I send some data to DAC with stm32f429-discovery(Master), DAC doesn't react. every other pin is doing as it should. it's like DAC is always busy. any help?

Thanks

  • 0
    •  Analog Employees 
    on May 8, 2016 4:59 PM

    Can you post a schematic or timing plot for your circuit? BUSY should work as you describe and I haven't heard of this happening before.

  • Hi. thanks for reply.

    This is what I see with Logic Analyzer..

    Zoomed in:

    Schematic:

    Sheet1.SchDoc

  • 0
    •  Analog Employees 
    on May 11, 2016 7:09 AM

    The scope plots look ok to me apart from Busy being low. I wasn't able to open the schematic file. Can you post it as a pdf or jpg?

    The zoomed in plot shows that you are setting the GPIO pin as an output and setting it high. Does this work.

    As you posted in a separate thread, /BUSY is a bidirectional pin. There is no need to configure this pin. If an external signal pulls /BUSY low, any writes you make to the AD5360 will not be implemented until /BUSY is allowed to go high. This is useful if multiple AD5360 devices are used. Each will have a slightly different busy time. Connecting all the /BUSYs together will hold off the update of the DACs until the slowest device is ready.

    If there is an external source pulling the /BUSY pin low no updates can take place. If you have something connected to the /BUSY pin can you remove it to isolate the pin. This should allow it to go high. If it doesn't try attaching a ~50K pull up resistor to DVcc.

    Are you seeing this issue on one device or multiple?

  • Hi again. Thanks for reply

    No, GPIO doesn't go high. I think because DAC is always busy I can't write to it..

    /Busy is not being pulled down or up by any external source, but it is always low for no reason.. even when I isolate everything in board from DAC, it is still low.. /Busy pin is connected to a GPIO pin of a board(stm32f429 discovery) and I configured it as an 40K pull-up input (input from stm32f4 view) and it is still low..

    I tried it with one device.

    here is schematic in pdf:

    Sheet1.pdf  (You can click on blue button/Slow donwload to download)

  • 0
    •  Analog Employees 
    on May 16, 2016 10:56 AM

    I don't see anything wrong with your schematic. It's possible that the AD5360 has been damaged in some way. Do you have another part you can try?