I have one 4 layer board with high accuracy Analog 18bit ADC on board.
Bottom left is USB with Power input, going up is the switching power supply and analog opamp and ADC,
Right side are all digital ucontroller and FPGA.
I need to get the lowest noise on the ADC, how should I manage the ground plane, Now I have the 2nd layer as ground plane.
The switching power supply ( I have both boost and charge pump in the lower left section) generate a lot of noise on the ground plane.
I was thinking star ground the PS ground at the USB ground. Use the USB ground as the star.
Separate the analog and digital ground, but there is few digital lines for analog conversion and SPI interface.
Need you comments.