AD8131 and AD9461


After a lot of research, i've narowed down my choice of components to an AD8131 to convert my singe ended signal to differential ended, and the AD9461 to perform the high speed conversion.

Now, i just a have some doubts around the "common mode" part.. i would be very grateful if someone from AD (or other experimented users) could back me up!

The application example of the AD8131 (PAGE 18) shows a VCM set to ~1.5V.

The AD9461 specify that the input common mode voltage should be around ~3.5V. I will be using the nominal 1.7 VREF.

1- In order to use both those circuits together, i'll need to raise the output common mode of the AD8131 to 3.5V, right?

2- In that same application circuit of the AD8131 (on PAGE 18), the IN+ is referenced to GND right? If that's the case, can i reference IN+ to another voltage simply by connecting IN- to another voltage, right?

3- I'll be connecting the output directly to an FPGA that is ~1 cm close. Does it still make sense to use differential output then?

Thanks a lot for your time

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  • Thank for your answer, ans sorry for my late reply.

    Yes, my analog signal is DC coupled (coming from a laser sensor) and will have a voltage swing of 0 to 1.8V.

    I working on implementing the AD9467 as you suggested with a AD5201, but i am confused on how to be sure that the full swing of my input voltage is covered (ex: 0V gives 0 ADC code, and 1.8 gives 0xFFFF ADC code).

    Is there any app note out there that can help me out?

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