The Importance of the RF Reference The RF Reference is the node on a circuit’s schematic that we define as our reference voltage when designing an RF circuit or measuring its performance. For the most cost-effective EMC, all circuits (digital, analogue, switch-mode, etc.) should now be designed using RF techniques. It is common practice to call the RF Reference ‘earth’ or … [Read more...]
Designing and Selecting Filters: How Filters Work
Ignoring all the poles and zeroes in the filter textbooks: filters work by creating an intentional discontinuity in the characteristic impedance of a current path, reflecting radio frequency (RF) energy away from a protected circuit, or absorbing the RF energy (converting it to heat) – rather like a shield does, as will be described in Part 4 of this series. The greater the … [Read more...]
Good SI, PI and EMC require this most of all…
Good SI, PI and EMC require a proper, grown-up understanding of electricity... Instead of what circuit designers are taught! As electronic designers, we were taught the children’s version of electricity at school, college, university, etc. This is the version that pretends (just as the SPICE simulator does) that electricity flows as little packets of charge totally inside … [Read more...]
Functional Safety, Risk Management, EMC and EMI
What is Functional Safety? The safety of products, systems and installations can be split into two parts: i) ‘Basic’ safety: electric shock, excessive temperatures, excessive radiation, fire, explosion, implosion, bruising, pinching, crushing, cutting, emissions of toxic fumes, etc. ii) ‘Functional’ safety: when things being controlled don’t function correctly … [Read more...]
EMC Confidence Checking
I was recently working with a manufacturer of stand-alone ticket machines, who had big problems with Ethernet-related emissions. Long story short – it was the Ethernet hub they had incorporated in their machine. They had assumed that all CE-marked Ethernet hubs would be equally good for EMC, and they had several different types lying around their design department. We tested … [Read more...]
Mains Harmonic Current Emissions are Always Bad – It is Risky to Rely on the Limits or Exclusions in the Standards
Many (perhaps all) of EMC standards that are listed under the EMC Directive, that set limits for mains harmonic emissions, have exclusions (‘let-outs’) for certain types of equipment, especially: (these examples are from IEC/EN 61000-3-2 Ed.5:2018) Lighting equipment with a rated power of less than but not equal to 5W Equipment with a rated power of 75W or less, e.g. … [Read more...]
ESD Testing Needs to Change to Reflect Real-Life
Semiconductor die shrinking means that 0.7ns risetimes are now too slow Electrostatic discharges in the real world cover a very wide range: from relatively slow high-voltage events (say, > 1kV peak) to extremely fast low-voltage events (say, < 1kV peak). The figure shown is of the transient field radiated by a micro-gap discharge between two coins – more on this … [Read more...]
Ground / Power Bounce Cause Noise Emissions From All IC Pins
Ground and power bounce are often ignored as sources of CM noise emitted from all integrated circuit (IC) pins, even if they are static inputs or outputs, digital or analogue, and even sometimes emitted as radiated noise directly from the body of the IC (especially when its physical structure resonates). CMOS ICs use ‘totem-pole’ logic switching gates that momentarily short … [Read more...]
Risks Associated with EMC and EMI – Don’t get Confused!
There are many kinds of risk For example: the risk of being late for an appointment; the risk of buying a lottery ticket but not winning a prize; the risk of designing and manufacturing a new product that might not sell well enough, etc. The above are examples of non-safety-related risks, but safety-related risks also exist. EMC1 Risk Management (or, the Risk Management … [Read more...]
A Simple Method for Estimating Radiated Emissions – Part 2
I recently published this blog, detailing a simple proven method for estimating the radiated E field with specified test setup. As a result, I received the following feedback... 'This model is wrong for equipment tested over a ground plane as described. The complex correct transmission line model (less the ground plane) is given by Balanis, and a simpler but accurate … [Read more...]