Tag
emc
6 articles.
- Switch-node ringing: measure it, then size the snubber
Two scope readings give the loop inductance and the parasitic capacitance. From those the snubber values follow, and so does the reason to fix the layout first.
- Measuring supply ripple: the ground clip is the antenna
A 3-inch probe ground lead turns a switching spike into ringing that is not on the rail. Tip-and-barrel, coax, bandwidth limits, and the null test.
- How a common-mode choke works, and where it goes on USB
How coupled windings block common-mode noise but pass the differential signal, how to read both impedance curves, and where the choke and TVS go on USB 2.0.
- Buck converter input filter design for conducted EMI
Size a buck converter's LC input filter from the required attenuation at the switching fundamental, damp the resonant peak, and keep the control loop stable.
- Should you split analog and digital ground planes?
One continuous ground plane with partitioned placement beats a split: where return current really flows, where AGND and DGND tie, and when a moat is right.
- Ferrite beads are not resistors, and the 100 Ω is not 100 Ω
A bead is useful in the middle of its curve, the rated impedance is one point at 100 MHz, DC bias collapses it, and before a capacitor it can amplify noise.