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AFE7950: MAX Full scale input power without affecting reliability of the device

Obul reddy
Prodigy 115 points
Part Number: AFE7950

Tool/software:

Hi Team,

we are using AFE7950 in our custom board and we wish to know the maximum input power we can give to AFE7950 device at 9.5GHz without affecting reliability of the device. we want to increase DSA to maximize peak input power. what is the maximum DSA setting I can use? and how much RF power I can give at that DSA value?

the datasheet says 23.5dB with 20dB DSA at 9.6HGz but the reliability will be affected.
can we know why reliability will be affected when DSA 20dB? what are the optimum settings I can use?

Thank you,

Obul

  • 0
    Prodigy 115 points

    Hi Team, any update?

  • 0 in reply to Obul reddy
    TI__Genius 17291 points

    Hi Obul,

    On the Rx side you can use the full 25dB DSA range, in 0.5dB steps.

    Please note that there are two specs for the ADC Full scale input power. The first is the minimum power required at the ADC input pins for full scale, with DSA=0. If the ADC input power exceeds this power level the reliability detector would trigger and set the DSA to max value in order to protect the ADC inputs. The difference in gain is compensated in digital and a flag would be available in either the status register or through a pin.

    The second spec, MAX Full scale input power (reliability limited), corresponds to the max RF input power that the AFE pins can accept, this is reliability limited and therefore should not be exceeded. 

     

    Regards,

    David Chaparro 

  • 0 in reply to David Chaparro
    Prodigy 115 points

    Thank you David for the reply,

    If we provide Max scale input(w.r.t DSA 20dB) and set DSA 20dB, why the reliability of the device affected? as the power will be with in the limit of ADC, the reliability should not come down.

    is it something to do with heat generated by DSA due to attenuation?

    or as we have already used 20dB DSA, AFE will not have cushion to use extra DSA when input power exceeds the Max scale value(to protect the device)?

    Thank you,

    Obul

  • 0 in reply to Obul reddy
    TI__Genius 17291 points

    Hi Obul,

    The reliability limit is the max power that the ADC pins can accept regardless of DSA. This should not be exceeded.

    Regards,

    David Chaparro