How to isolate power supply noise from I/O modules

Isolating power supply noise from I/O modules is crucial for system stability. A multi-stage power architecture should be employed. The primary input power supply should first pass through an EMI filter, which includes a common-mode inductor and X/Y capacitors, such as a power module with an integrated filter. A DC-DC isolation converter is then used to completely isolate the noisy primary ground from the clean secondary ground; the isolation voltage should be selected from 1.5kV or 3kV and above, depending on the application requirements. On the secondary power side, independent LDOs or switching regulators should be configured for different functional circuits, such as separate power supplies for analog circuits, digital cores, and interfaces, to avoid noise coupling through the power path. Decoupling capacitors should be placed near the power pins of each chip to form a full-band decoupling network from high to low frequencies. For particularly sensitive circuits such as high-precision ADCs, an additional LC filter or active filter can be used. In PCB layout, different power domains should use segmented power planes and be connected at a single point using ferrite beads or 0-ohm resistors to control noise propagation paths. Simultaneously, power traces should be as wide and short as possible to reduce voltage spikes caused by parasitic inductance.