How to control power ripple in I/O modules

Power ripple in control I/O modules requires multi-stage management, encompassing the source, transmission, and load. Switching power supplies are the primary ripple source; therefore, low-ripple output models should be selected, and a two-stage LC filter should be added to their output. PWR series power inductors can be used. On the power distribution network, local decoupling capacitors should be configured for each load chip. Large-capacity electrolytic or tantalum capacitors should handle the low-frequency band, while multiple small-capacity MLCC capacitors should cover the high-frequency band, forming a low-impedance power network.

For noise-sensitive circuits such as PLLs or ADCs, LDOs can be used for secondary regulation, as LDOs themselves have good ripple suppression capabilities. In PCB design, the power plane should be as complete as possible and tightly coupled to the ground plane, forming natural distributed capacitance. Power traces should be wide to reduce voltage drops and noise caused by parasitic resistance and inductance. For high-current dynamic loads, a point-of-load (POW) architecture can be used, with the addition of large-capacity energy storage capacitors to handle instantaneous current demands. Ripple levels can be accurately assessed using ripple probes and oscilloscopes, allowing for targeted filtering of key spectral components.