I am designing a four layer PCB, (signal, ground, pwr, signal), which is to generate +-1V max 30kHz frequency signals which is output on a differential pair. It is pretty simple board layout but I am little confused about whether I should use a split ground or even slit the board. My board layout can be seen below.

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There seems to be alot of debate over the benefits or possible problems of what a split ground might do. My plan for the board is to have the left half dedicated to the output signals, powered by two regulators +3.3V and -3.3V. I have a 2MHz clock that generates the clock for frequency generating chips, AD9106 x2. I am worried about this potentially contaminating the analog signals. Additionally I have placed ferrite beads (MPZ1608B471A) on the output of each of the regulators to stop this, I have employed good decoupling capacitors where required.

Any hints or tips on what grounding scheme may be best would be appreciated.

  • \$\begingroup\$ How clean must your output signals be? \$\endgroup\$ – analogsystemsrf Nov 30 '18 at 3:38

Splits or cuts in ground planes generally create more problems than they solve. Placing components strategically so the digital signals avoid the analog section is the best approach. Digital signals should be routed so that their ground return path does not go through the analog section. Also proper design of both the digital and analog power delivery network to reduce power supply noise from propagating through the board is helpful. In addition to ferrite beads, Linear regulators on the analog power supplies can help to reduce noise. Another thing you can do is to control the rise time of the 2 MHz clock by using an RC network. Since 2 MHz is a relatively low frequency, you don't need a fast rise time.


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