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Original question:

ADS52J65: ADC RF input impedance question

ADS52J65: VCM , Analog input FS

Yair Amran
Prodigy 10 points
Part Number: ADS52J65

Tool/software:

Dear TI team 

I have some question about the Analog input in ADS52J65

In the datasheet  file

 

 

Page 29

“For a full-scale differential input, each input pin INP, INM must swing

symmetrically between VCM + 0.5 V and VCM – 0.5 V, resulting in a 2-Vpp differential input swing.”

 

But (VCM + 0.5 V) – (VCM - 0.5 V) = 1V not 2-Vpp

Same recommendation in page 7

 

 

Page 6

Absolute Maximum Ratings

Voltage applied to

analog input pins AINMx, AINPx        –0.3       minimum ( 2.2, AVDD_1P8V + 0.3 ) V

 

If VCM = 0.9V the maximum  AINP , AINM as in page 29 will be 1.4V

 

Our input signal is from power detector Vhigh = 1.27V Vlow = 0.47V swing of 0.8V

 

  • 0
    TI__Expert 7685 points

    HI,

    “For a full-scale differential input, each input pin INP, INM must swing

    symmetrically between VCM + 0.5 V and VCM – 0.5 V, resulting in a 2-Vpp differential input swing.”

     

    Ex :VCM is 0.9 .. This means INP will swing from 0.4 to 1.4 and inm will swing from 1.4 to 0.4 . (Each is 1Vpp) . Differentially it will be 2Vpp. Max voltage is 1 V when inp is at 1.4V and inm at 0.4V . Min voltage is -1V when inp at 0.4V and inm at 1.4V .