We are having trouble getting the ADCMP572 to receive a 400mVppdiff signal running at 2.7Ghz without disturbing the serial link it is attached to (see attached diagram).
Questions about ADCMP572 input:
1) What DC bias do inputs want to
operate in middle of CMR?
2) What is Vinmin?
3) What is the structure of the input?
I have the same question, I am using this as the input stage for a high frequency counter and need to ac couple the inputs. Does the chip provide a mid rail DC bias? If not what is the recommended circuit for applying a DC bias to the inputs for detecting a zero crossing without referencing ground to a negative voltage?
ScottH can you look into this question please?
Hi lallison. I am not an expert on the ADCMP572, but I will ask the appropriate expert to follow up. Thank you.
There are two ways you can introduce a DC bias to the inputs.
First, if you have another dedicated voltage source, you can force the DC bias through the VTN/VTP pins as shown on the figure below. For example, if you have the VCCI set to 3.3V, the middle of your input range is at 0.5V (input range is -0.2V to 1.2V for VCCI=3.3V).
Another way is to use a voltage divider with its center connected to the VP/VN pins. The voltage divider should also have an impedance equivalent(R1 in parallel with R2) to 50ohms for impedance matching. So for VCCI=3.3V, the value of R1=R3=383ohms and R2=R4=57.6ohms.