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AD5611 analog output

Category: Hardware
Product Number: ad5611

Hello All,

I am working with AD5611. I wrote a code to adjust output of AD5611. When I try to send 466 decimal to AD5611 the scope screen capture is as follows.

Yellow is SYNC bar, Blue is CLK, Purple is SDIN and Green is out of AD5611. Some how on 8th falling edge DAC updates its output. I could not understand that?

Top Replies

    • in reply to dclm +1 verified

      Hi,

      The new one has same response

      On the same or different board?

      The slow signal transition at the output of the optocoupler can also be a problem. The datasheet says: "All input signals…

    • I did couple of more tests it seems that AD5611 outputs differ time to time.

    • 0
      •  Analog Employees 
      •  Super User 
      in reply to dclm

      Hi  

      This is an unusual response. Are you using eval board or custom hardware? can you share the schematic? What's the VDD voltage level? Clock frequency?

      On the first plot, dec 466 should output to 2.27V, assuming 1V/div, the change is around 2.5V. did the output settle on 2.27V after the spi write? around 10-20us after sync high what is the vout voltage?

      Best regards,

      Ian

    • Hello Ian,

      I am using custom hardware that I made. The schematic is as follows. R7 is not populated. Output is floating right now.

      Voltage for AD5611 is 5V. I use ADR435 to supply 5V. My clock frequency is around 166Hz.

      Output does not follow any logic right now. If I send 466 Sometimes I get 2.27 sometimes 80mV. Output stays like that does not change. When I set logic high the sync pin nothing happens. When I power up board and send first 16 bits sometimes nothing happens. sometimes after 6 th clock output update itself. sometimes 8th clock cycle. sometimes output changes on rising clock cycle too. I am hand soldering the IC. Maybe I damage the component but I am not new to hand soldering.

    • Hi,
      Are these signals measured directly on the pins of the DAC? I would check the soldering and the connections, this kind of problem can be caused by unreliable contacts.
      Zoltan

    • not at all. On R10, R1 and R5 resistor pins. DAC5611 has very narrow pins I can not measure directly on DAC5611. I have changed the IC with a new one. The new one has same response. So I guess it is very unlikly to damage both IC's

    • Hi,

      The new one has same response

      On the same or different board?

      The slow signal transition at the output of the optocoupler can also be a problem. The datasheet says: "All input signals are specified with tr = tf = 1 ns/V (10% to 90% of VDD)", although no maximum rise/fall time is specified.

      Check if it works without the optocouplers.

      Zoltan

    • Hello Zoltan,

      On the same board. I have changed the 20K to 4.7K still same. But maybe it has some effect. I have tested couple time and output changes on 12th and 9th pulse.

      rise time for 4.7 K

      Output change at 4.7K

    • I have changed 390R to 270R and R1 to 1K. Now it works. This is current rise time. Signal rise time slower than this can cause problem. Datasheet must inform users I have lost 2 days working on this. I used AD7391 for over 10 years and did not face such a problem. 

    • Hi  

      I'm glad to see that the problem has been solved.

      I always have some doubts if a slowly changing signal drives a logic input, even if it has Schmitt-trigger inputs. You're right that it should be more explicit in the datasheet. 

      Best wishes,

      Zoltan