Debugging Signal Integrity on a Custom PCB
Lessons learned from oscilloscope probing, ground-loop isolation and decoupling-capacitor placement during analog-digital interface bring-up.
Bring-up of a custom PCB is where theoretical knowledge meets the bench. The first probe touch usually reveals what schematics cannot: ringing, ground bounce, and crosstalk that no SPICE simulation flagged.
Methodical isolation - one rail, one signal, one stage at a time - narrowed the issues to two root causes: an underdamped clock trace and a shared return path between analog and digital ground islands.
The fix was unglamorous: a series termination resistor, a cleaner ground-pour cut, and a tightly coupled decoupling capacitor at the supply pin. The lesson endures: signal integrity is engineered at layout, not patched at debug.
By Tal Moyal · Hardware, FPGA & RTL Design
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