How can high-frequency devices in Human-Machine Interfaces (HMIs) be kept away from sensitive circuits?

In HMI PCB layout, keeping high-frequency devices away from sensitive circuits is the most direct and effective way to reduce noise coupling. High-frequency devices include switching power supply chips, DC-DC converters, clock generators, high-speed transceivers (such as Ethernet PHYs), memory buses, etc., which generate strong electromagnetic fields. Sensitive circuits include analog sensor inputs, high-precision ADCs/DACs, microphone preamplifiers, touch sensing circuits, phase-locked loops, etc. During layout, functional partitioning should be performed first, clearly defining high-frequency noise areas and sensitive quiet areas on the PCB. Maintain as much distance as possible between the two areas, typically at least 2-3 cm, using ground planes or power planes as isolation strips, or even physical slots for isolation (but be aware of the impact of slots on return paths).

Place high-frequency devices as close as possible to the board edge or interfaces, while placing sensitive circuits in the center of the board or away from noise sources. Crystal oscillators and clock lines must be strictly kept away from analog input pins. If space is limited and cannot be avoided, local shielding must be used to shield high-frequency devices or sensitive circuits. Furthermore, the power supply to high-frequency devices must be adequately filtered before supplying power to sensitive circuits. By implementing strict layout partitioning and isolation measures, and utilizing the shielding materials and filtering devices of Audiotech, the interference of high-frequency noise on sensitive circuits can be minimized.