serial d/a converter

Discussion in 'General Electronics Chat' started by milos, May 6, 2007.

  1. milos

    Thread Starter New Member

    May 6, 2007
    4
    0
    Hi there,

    I am using serial d/a converter (AD5432 from analog devices) for the first time and have some problems with it. I designed the circuit for unipolar output according to datasheet and i am controlling the control words with FPGA.
    However, i am not getting any output (0V). I was thinking that the problem might be in setting the control words correctly. I know that it is time consuming for someone to go through the datasheet of this component so I am asking if anybody used this or any other (since they all work similarly) serial DAC before?
    Also can i use constant voltage for Vref using power supply generator or that doesnt provide good stability, etc?

    Any comments in this metter will be very much appreciated.

    Thankx

    milos
     
  2. John Luciani

    Active Member

    Apr 3, 2007
    477
    0
    The AD5432 is a multiplying DAC. What are using for an output op-amp?
    What are using for a reference? Since you are using a 10bit DAC you should
    use a reference not the power supply.

    It would be helpful if you post a schematic of the DAC section of your circuit.

    (* jcl *)
     
  3. milos

    Thread Starter New Member

    May 6, 2007
    4
    0
    Hi John,

    Thank you very much on the reply.

    I sent the schematic of my circuit in the attachment.

    For the output op-amp i am using AD8065 as recommended from the datasheet.

    What I meant for reference is that, in datasheet they are using ADR01 precision 10V voltage reference, in my case I am just using constant voltage generator of +10V (like battery) for Vref and I have separate power supply of +5V to power on the chip.
    I dont think that can infulence the result at the output. I might not get maybe the accurate analog waveform but at least i would get something.
    Even when I feed constant digital word to DAC for purpose of testing I dont get anything at the output.

    From the datasheet it says that this DAC has to be fed first with constant word like 1001 (for Load and Update) and then data bits. I am doing this as well but again it is not giving me anything at the output.

    Any suggestions?

    Thankx

    milos
     
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  4. John Luciani

    Active Member

    Apr 3, 2007
    477
    0
    Are you using a positive and negative power supply on your output opamp?
    I believe that the output of your configuration is Vout = -Vref(CODE/1024).

    If the reference voltage is at 10V, you have a bipolar supply on the opamp and your connections are as you have shown in the schematic you probably have a timing problem. You need to verify the timing matches the timing diagram.

    (* jcl *)
     
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