• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 46 subscribers
  • Views 622 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DDC112 IS NOT RESPONDING

subhabrata mazumder
Prodigy 150 points
Other Parts Discussed in Thread: DDC112

I am trying to interface DDC112 with ATMEGA32 micro controller but no dvalid signal is coming from DDC112.The steps are given below:

1. AVdd and DVdd are tied up together to 5V supply.

2. 7.5MHz is given to DDC112.

 3. TEST pin is high and CONV is toggling 1ms time interval.

4. Range0 to Range2 pins are at logic high level.No external capacitor connected.

5.DXMIT  at high logic state and DCLK,DOUT at low logic state.

In this case DVALID signal coming from ddc112 is always at high logic state.Please help me out .....   

  • 0
    TI__Guru 65410 points

    Hello subhabrata,

    Thanks for contacting TI. I am Adam Sidelsky, applications support for the DDC products.

    Your points above seem correct. For data readout you will need to control DXMIT and DCLK but for now you should be seeing DVALID going low once per conversion to show that the data is ready. How are you measuring DVALID? DVALID doesn't go low for long so I would verify it with a scope and make sure that your micro isn't pulling it high, missing the pulse, or something similar. 

    Have you checked your Vref voltage is around 4.096V?

    Are you synchronizing the CLK and CONV signals? It is recommended that CONV toggles within +/- 10nS of the rising edge of CLK.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 150 points
    Thanks for your reply.I am watching DVALID signal with an oscilloscope.CLK and the controller CONV both are connected to a D flipflop to generate actual synchronized CONV signal for the DDC112 .Vref is absolutely OK.It is generated using REF3040 IC as per your datasheet.Inputs are open condition and test is in high still no DVALID is coming.
  • 0 in reply to subhabrata mazumder
    TI__Guru 65410 points
    subhabrata,

    I checked again and still I believe you have everything correct. Have you tried on more than one board or more than one DDC112? Have you verified all your signals at the pins of the DDC112?

    If you pull DXMIT low and toggle DCLK, do you see any change on the DVALID signal?

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Prodigy 150 points
    Hello Adam,
    I don't have extra DDC112 chip.So it is not possible for me to check with other DDC112 chip.After pulling DXMIT low and toggle DCLK ,there is no change in DVALID pin.