Marko Marin, Technical Account Manager at Ansys, stopped by our booth at DesignCon to answer a few questions about signal integrity.
One of the major concepts in electronics is the printed circuit board or PCB. It’s so fundamental that people often forget to explain what a PCB is. Electronics have come a long way. A journey that started with vacuum tubes and relays got its way into silicon and ICs. It became more prevalent in consumer goods. Therefore, there is always pressure to reduce the size and manufacturing costs of electronic products. This drove manufacturers to look for better solutions.
Controlled impedance printed circuit boards (PCBs) often include a measurement “coupon”, which typically includes sample traces, 6 inches long and constructed as part of the printed circuit board panel. They are measured to assure the PCB stack-up and the accuracy of the PCB transmission lines. These coupons, as well as the actual PCB signal traces, interconnects and cables are typically measured using a Time Domain Reflectometer (TDR). A TDR is generally a large, expensive instrument that includes a high-speed edge pulse and a sampling oscilloscope.
From signal integrity to roughness of the copper and stack-up design, here are a few PCB design tips you could use:
- Insertion loss and attenuation
- Signal integrity for automotive electronics and IoT
- Fine lines
- Copper for ground and power planes
- Roughness of the copper
- Stack-up design
- Work with your fabricator
The topic of clock jitter performance seems to be a current focus of clock, ADC, and power supply manufacturers. The reasoning is clear; clock jitter interferes with the performance of digital circuits including high speed ADCs. High speed clocks can be quite sensitive to the “cleanliness” of the power they receive, though quantifying the relationship takes some effort.
After reviewing the differential impedance as well as the even or common mode, let’s now dive into the physical parameters of a differential pair.
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