How to reduce high-frequency clock noise in HMI (Human Machine Delivery) systems?

Reducing high-frequency clock noise in HMIs requires a multi-pronged approach, addressing the clock source, transmission path, and receiver. First, select a clock generator with low jitter and a moderate edge rate, as excessively fast edges generate abundant high-order harmonics. Strict decoupling should be implemented on the clock chip's power pins using parallel 0.1μF and 1μF MLCC capacitors, and a small ferrite bead, such as the PBZ1005E121Z0T, can be connected in series on the power lines to filter out power-introduced noise. Clock signal traces should follow transmission line rules, with impedance control, routing them on inner layers and referencing a complete ground plane, avoiding crossing split planes. Connecting a small resistor, such as 22Ω-33Ω, in series on the clock lines can effectively slow down edges, suppress overshoot and ringing, thereby reducing high-frequency radiation.

If possible, use differential clock signals, such as LVDS format, and pair them with CMZ series common-mode chokes to suppress common-mode radiation. For clock drivers fanning out multiple loads, clock distribution chips should be used instead of simple T-connections to reduce reflections. Locally isolate the clock circuit area using ground lines or shielding to prevent noise coupling to other circuits. Identify clock harmonic exceedance points through spectrum analysis and use targeted absorption filters, such as three-terminal capacitors or ferrite beads. Etymotic's PBZ series high-frequency ferrite beads have excellent noise suppression effects in the 100MHz to GHz frequency band and can be used for power supply filtering of clock lines and drivers.