W5500 Ethernet Module Harmonics Exceeded?

100M Ethernet products with excessive low-frequency emissions get projects stuck in EMC testing in minutes! Don't panic! Spare no effort to organize 6 solutions, according to do easy to pass the test ??!

1?? Crystal Circuit Checking

?? Crystal selection is key!

- Recognize the module's official recommended model! Choose a stable frequency, low harmonic crystal, miscellaneous crystal is a “minefield”

- Measurement: After replacing a brand crystal, 100M harmonic intensity dropped 20dB!

?? Filter buffs stacked full

- Add RC filter (resistor+capacitor combo) on input and output to intercept stray waves

- Clock lines must be π-filtered! Two-stage filtering directly cuts off the harmonic propagation chain

?? Layout guide to avoid pitfalls

- Keep crystals away from high-frequency signal lines, at least 3 times the line width

- Add a grounding protection ring! Draw a “moat” for the crystal to block the spread of harmonics!

2?? Filter Circuit Upgrades

??? Low-pass filters are a godsend!

Solder a low-pass filter around the crystal, specializing in high-frequency harmonics! Measurement can suppress more than 3rd harmonic.

Decoupling capacitor “special forces”.

- Add 0.1μF+10μF combination capacitor between power/ground, high-frequency and low-frequency noise in one pot.

- Capacitors should be close to the chip pins! The farther away, the weaker the effect.

3?? Grounding Design “Lifeline”

?? Three elements of grounding

- The module ground pin must be short and thick and directly connected to the main ground! Avoid “false grounding”

- The larger the area of copper, the better! A complete ground plane absorbs 80% of harmonic radiation

- Multilayer boards are preferred to use the inner grounding layer for full shielding effect.

4?? Physical defense is full

?? Metal Shield YYDS

Solder a metal shield to the module and crystal, and solder the ground! Instant “electromagnetic cage”.

?? Network Transformer Replacement

- Change different brand/built-in multi-core transformer, measured a certain model harmonic reduction of 15dB

- Separate isolation of module power supply! Use DC-DC to isolate the power supply and cut off the interference conduction path.

5?? Software Optimization “Black Technology”

? Clock Configuration Adjustment

- Turn off non-essential peripheral clocks to reduce signal interference

- Fine-tune the clock frequency division parameters to avoid sensitive frequency points

?? Power management metaphysics

Optimization of standby mode power consumption, measured 20% reduction in power consumption, harmonic intensity followed by a drop!