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ADC12DJ3200: Calculation of Full Scale Range on Each Inputs

Jaydip Jani
Prodigy 10 points
Part Number: ADC12DJ3200

Hello,

I was trying to calculate relationship of input power to Converter's(ADC12DJ3200) sample power. I Got stuck at exact full Scale voltage (Vpp) Number .

In the current system, Register Setting of 0x031 0x030 as  0xA4 & 0xC4 respectively.

I tried to map through linear equation, but found that example points given in datasheet is not linear.

Kindly suggest if i am missing any information.

Thanks,

Jaydip

  • 0
    TI__Genius 12780 points
    Hi Jaydip,

    One of our experts is reviewing your question, and will be back with you shortly.

    Best Regards,

    Dan
  • 0 in reply to dBrock
    TI__Mastermind 43950 points

    Hi Jaydip

    It is possible to create a linear equation to convert from FSR register setting to mVpp. The default FSR setting of A000h (40960d) gives a full scale input range of approximately 800mVpp differential. From this other values can be calculated ratiometrically.

    To calculate the input RF power requires converting the Vpp value to Vrms, and then calculating the power into the ADC input impedance (approximately 100 ohms differential).  Note: This calculation is only valid if the input is sinusoidal.

    Therefore we have the following for the default and your example FSR settings:

    •Default FSR A000h or 40960d gives typical 800mVpp diff
    •Customer Setting A4C4h or 42180d gives typical 832.83mVpp diff
    •ADC input impedance is 100 ohms
    •Power into 100 ohms calculation
    –Power = V^2/R (must use Vrms rather than Vpp)
    –Divide Vpp by 2√2
    –Pdefault = (0.8/(2√2))^2/100*1000 = 0.8mW
    –Psetting = (0.83283/(2√2))^2/100*1000 = 0.867007mW
    •Power in dBm
    –Pdefault = 10log(0.8) = -0.9691 dBm
    –Psetting = 10log(0.867007) = -0.61977 dBm
    When using the ADC12DJ3200EVM please also keep in mind that the balun used has a fairly high insertion loss (6dBm typical), so the power applied to the board, which is the input to the balun is around 6dB higher than what is present at the ADC input.
    I hope this is helpful.
    Best regards,
    Jim B