AEi Systems 2013


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8 of 10 Design Issues I Find Are Due to A Single Problem Steve Sandler, AEi Systems	Latest News & Articles
The vast majority of design issues are directly or indirectly attributable to control loop stability. The most common offenders: Linear regulators Voltage references Op-amps The control loop stability of these devices can propagate through an entire system. Symptoms include: EMI Increased circuit noise Clock jitter These are all simple circuits, so why is this a common issue? We are not clear on the definition of stability In the high-reliability world, including satellite systems, where I do most of my troubleshooting, stability means a minimum phase margin of 30 degrees and a gain margin of 6dB at the end of life, including all component variations and environmental factors. There are guidelines that define the stability margin limits, and one of our tasks is to ensure that margin. This requirement is not well aligned with the information given out by manufacturers. They generally do not provide quantifiable metrics for the stability of their devices. In many cases, the devices will not meet a 30-degree phase margin even typically when coupled with low-ESR capacitors. The definition of stability in the semiconductor world seems to be whether the circuit has a stability margin that is greater than zero. Component manufacturers drive us to it through recommendations In some cases, manufacturers provide recommendations. One example I often use is the REF02 voltage reference. The manufacturer's datasheet highly recommends the addition of a 0.1uF output capacitor on the voltage reference. Read More...	News AEi Adds RH1959 SPICE Model New Articles How do I pick the best voltage regulator for my circuit? Why is PDN measured using a VNA and not an oscilloscope? Common Oscilloscope Usage Mistakes How to measure PSRR of a linear regulator? New Videos Why Stability Matters Impedance Is the Critical Measurement Measuring Impedance - 1 and 2 Port Measurements
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