Hi,
I'm using ADC34J23 in my design. The target frequency is 327MHz, so I adopted the circuit design for High Input Frequency(Fin > 230MHz) in the datasheet(Figure 206).
However, the ENOB of the actual product is very bad, and I found the input signal gets so much noise at the resistor just before the IC input pin(10Ω resistor in Figure 206) using a differential oscilloscope.
I've been investigating the cause and realized the circuit design in the datasheet is a little different from the evaluation board.
There is another part(25Ω resistor, 10pF capacitor, 56nH inductor) between the 10Ω resistor and the IC input pin on the evaluation board for high input frequency.
Why are they different? Does this difference cause noise to an input signal?