Issue with my ad7609, busy signal o/p..

I have interfaced the AD7609 in parallel to a TMS320F28335 GPIO's. I have a problem with ADC busy o/p. When CONVST is Active(High), Busy should be Active(HIGH) and after Tconv(8-channel conversion), Busy should get a High to Low Transition. Till this stage it is working as expected. But, after the Busy High to Low Transition, the CONVST is made low, and all the CS & RD pulses for o/p data are given. The problem is when CONVST is made low, busy isn't getting LOW and when 2nd time CONVST is made active(High) the busy is expected to get a high to low transition, which is not happening. The busy is remaining in High state.

I have used a 70mm length Bus for Data lines & Control signals. Using the 10V range in parallel Interfacing mode and the 5v supply is from power supply and 3.3v supply is from TMS320F28335.

Please reply as soon as possible..it is a scheduled task and i am stuck with it.

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  • Hi Steven,

    Thankyou for your response.

    1.

    StevenX wrote:

    Could you make the issue more clear ? After power up, one CONVST pulse is applied, the BUSY keeps high forever, right?

    This problem is solved. No more issue with Busy output.

    2.

    StevenX wrote:

    To be simple, please pull /STDY to VDrive through 3.3kohm resistor and OS[2:0] pins to Ground. Then, power up the board, apply the RESET pulse, wider than 50ns, as specified in datasheet. check the function of CONVST and BUSY. It is better the waveform capture of CONVST and BUSY by scope can be provide.

                         As you have suggested, I have connected /STDY to VDrive through 3.3kohm resistor and OS[2:0] = 0,(No Over Sampling).

         RESET pulse is 5ms(>5ns)

    Now the resulting scope waveforms for CONVST, BUSY & FIRSTDATA o/p's :

    CONVST = 4.4us for OS=0.

    BUSY = 3.6us for OS=0.

       BUSY & FIRSTDATA o/p : FIRSTDATA = 3.6us.

    Till this it is working fine but for input & output I have problem.

    The analog input is given 2Vpp, 500mHz from Function Generator to CHANNEL 1, and all other Channel 2 to Channel 8 are grounded.


    18-bit Digital Output is converted from 2's Complement form to voltage using the calculation:

    // converting the 2's complemented binary result to corresponding voltage

                if(array[i] <= 0x1FFFF)

                    {

                        array[i] = (array[i]*2)/13107.2; // for 10v range (numerator*2)

                    }

                else

                    {

                        array[i] = 0x3FFFF - array[i];

                        array[i] = (array[i]*2)/(-13107.2);    // for 10v range (numerator*2)

                    }

    Output from all channels is stored in 'array' for 1 conversion: (CCSv4)

    And this is not constant for next RUN. Value changes time to time which should not happen actually.

    Please help me with this issue..

    Thank you.


  • May I know, how did you solve the issue ?

     I am currently facing the same issue, AD7606 Busy is always LOW

    1] We are providing RST pulse [high and low] after power up

    2] Our Controller is powered first, then the ADC

    3] CONVA and CONVB are shorted as CONV, and a low to high edge is provided to ADC, but we are not getting any response from ADC i.e BUSY is always low

        a] CS and CLK are not provided to ADC until we conversion completes i.e BUSY going high and then low

         [Our case, BUSY is stuck at 0] 

    4] STBY is conn via 1k to VDRIVE [5V]

    Please provide your crucial feedback

      

Reply
  • May I know, how did you solve the issue ?

     I am currently facing the same issue, AD7606 Busy is always LOW

    1] We are providing RST pulse [high and low] after power up

    2] Our Controller is powered first, then the ADC

    3] CONVA and CONVB are shorted as CONV, and a low to high edge is provided to ADC, but we are not getting any response from ADC i.e BUSY is always low

        a] CS and CLK are not provided to ADC until we conversion completes i.e BUSY going high and then low

         [Our case, BUSY is stuck at 0] 

    4] STBY is conn via 1k to VDRIVE [5V]

    Please provide your crucial feedback

      

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