AD9262 Analog to digital converter input range

Question

Hi, 
 
 In the data sheet of AD9262 it is given that the common mode voltage of the ADC is 1.8V typical and 2 V p-p is the input span so considering that I would give a differential input, the input should range from 0.8 V to 2.8 V due to the Vcm value. But, it is also mentioned in the data sheet that the Vref of the ADC is 0.5 V. Isn't Vref the max value that ADC can convert to digital? If so then how will I give the input range from 0.8 V to 2.8 V and expect the ADC to convert it into digital? Or is my understanding totally wrong? What is the allowed input range of this ADC? Also is it possible to get the SPICE model or netlist for this product? Thank you in advance. 
 
 Best regards, 
 Tejaswini

PeeveeS · Accepted Answer

Hi Tejaswini, Thank you for your interest in AD9262. The allowed input range is 2Vpp diff. The Vin+/- pins will expect 1Vpp ranging 1.3V to 2.3V which will result in a 2Vpp differential input 
 Tej05 said: Isn't Vref the max value that ADC can convert to digital? If so then how will I give the input range from 0.8 V to 2.8 V and expect the ADC to convert it into digital? Or is my understanding totally wrong? 
 Looking at the voltage reference loop from the datasheet. The reference is used to generate a bias current. This loop makes it possible to convert 2Vpp differential input even though the Vref is only 0.5V. If you want to visualize how Sigma Delta ADC works, check this link. Sigma-Delta ADC Tutorial | Design Center | Analog Devices Best regards, Peevee)

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AD9262 Analog to digital converter input range