Podcast Episode Details
Back to Podcast Episodes#704 – Applied Embedded Electronics with Jerry Twomey
Welcome Jerry Twomey (Effective Electrons) author of the book, Applied Embedded Electronics: Design Essentials for Robust Systems. Chris first heard Jerry on Embedded.fm last year.
- Jerry’s Background and Book Motivation: Jerry shares his quick history, moving from the Boston area to San Jose (Silicon Valley) and eventually to San Diego, where he has worked across diverse sectors including consumer electronics, aerospace, defense projects, DARPA research, and medical electronics. His book focuses on how to develop robust systems, providing guidance that is timeless rather than applications manuals that quickly become outdated.
- The Analog Problem: Although modern systems may be digital end-to-end, Jerry emphasizes that the predominant causes of failure and design difficulties are often analog in nature. Academic study often teaches ideal signals but neglects real-world issues like inductance, noise, and cross-coupling.
- Consulting Experience & Troubleshooting: Jerry discusses being called in to fix systems that failed strenuous regulatory testing for medical devices, where reliability is first and foremost (similar to an aerospace way of thinking). Failures often stemmed from basic issues like a lack of ESD protection, absence of error correction in data streams, insufficient detection of errors, and common mode noise rejection problems.
- High-Speed Data and Signal Integrity: At high data rates, communication becomes a “communications channel problem,” not truly a digital one. When bits are underneath a tenth of a nanosecond, the communication turns into multiple standing wave transitions. The two primary limits on performance are rise and fall times and distance traveled.
- Real-World Applications: Jerry has worked extensively on medical devices, including early-generation Dexcom glucose monitoring systems (two on-body monitors and a hospital insulin pump/monitor), and a wearable EEG monitor. He also worked on a system that required packing five video cameras into an endoscope distal head, measuring 11 mm in diameter and 13 mm long.
- Architecting Systems and Identifying Bottlenecks: When starting a new project, Jerry suggests defining needs and interfaces and looking at the system as a black box. Engineering time should focus on the bottleneck—the hardest part of the system. For medical implantables, this might be minimizing power consumption down to virtually nothing, which could take up 90% of the effort.
- Power System Design: Jerry advises purchasing commercial AC-to-DC converters due to competitive pricing. He notes that switching supplies (buck converters) commonly introduce noise that can lead to EMI failures or corrupt sensitive analog front ends. A classic case of “digital thinking in an analog scenario” is when a sensitive analog front end is powered by a noisy switching converter.
- Working with Embedded Teams: Jerry prefers guiding embedded teams toward “self-discovery,” using bench time and empirical measurement (such as comparing grounds on a scope) to demonstrate non-ideal connections and grounding issues. He advises against the “seagull manager” approach.
- Grounding Best Practices: For integrated circuits (chi
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