AD9283 single ended input usage

Hello,

I would like to ask about AD9283.

AD9283 will be used with single ended input (\AIN is open). At this time, how change about Table I Output Coding (VREF=1.25V) in Datasheet?

I suppose AIN input range change to 0V...1.25V. Then when AIN=0V, Digital output is 0x00. When AIN=1.25V, Digital output is 0xFF.

My understanding is correct?

Thank you for your help in advance.

Best regards,

Sofy

  • 0
    •  Analog Employees 
    on Apr 16, 2014 11:32 PM

    Hi,

    The AD9283 is specified and described as a differential input device, with the nominal input range being 1.024V.   The output encoding table is for thi differntial voltage (AIN - \AIN).  We do not have any performance data for using it with a single ended input signal, but it should be possible.  The swing on AIN would be the +/-512mV about the 0.3*VDD input common mode voltage.  According to the data sheet pin descriptions, the |AIN pin can be left floating, but it is recommended to be connected to a 0.1uF capacitor and a 25 ohm resistor in seried to ground for impedance matching to the AIN input (assumes a 50 ohm source driving AIN). 

    Regards,

    David

  • 0
    •  Analog Employees 
    on Apr 17, 2014 6:47 AM

    Hello, David-san,

    Thank you for your response.

    I understood that. But I would like to ask one more about common mode voltage on Datasheet.

    According to AD9283 data sheet page 2, common mode voltage range is described +/- 200mVtyp.

    I suppose this range not suit for 0.3xVd biased that is described as a peak performance condition for Analog Input on data sheet page 8.

    Thank you for your help.

    Best regards,

    Sofy

  • 0
    •  Analog Employees 
    on Apr 17, 2014 5:40 PM

    Hi,

    The +/-200mV is relative to 0.3*Vdd, which would be 1V +/-200mV.  That is for a differential input.  At the recommended 1V Vcm , that would mean that the 1Vp-p  signal on each input would be 1V +/-0.25V.  With a single ended input the AIN input would be 1V +/-0.5V.  That increased swing would probably mean degraded distortion performance, and the even order distortion would likely increase compared to a differential signal which inherently has suppresses even order distortion. It possible that a higher common mode might be better for a single ended input, but the product was not characterized under that condition.  I would recommend converting your signal to a differential input if you want to realize data sheet performance.

    Regards,

    David