Engineering research, published openly

Average current, not peak MIPS, decides how long a sensing node lives. This note walks through the arithmetic for four common duty cycles, shows where datasheet sleep figures mislead, and gives a measured comparison of eight candidate parts under an identical one-per-cent duty workload with the same radio and sensor attached.

Datasheet bias-stability figures are quoted at room temperature on fresh parts, which is not how industrial equipment ages. We cycled forty six-axis IMUs from four manufacturers between minus 40 and plus 85 degrees Celsius for 500 cycles and re-characterised bias, scale factor and cross-axis sensitivity after each 100. Gyroscope bias degraded three to eleven times faster than the accelerometer channel, and the ranking between manufacturers changed after cycle 200, so a selection made on fresh-part data can be wrong within a year of field service.

Layout-induced gate-loop inductance remains the dominant cause of false turn-on in fast GaN half-bridges. We measure sixteen board revisions across a 3 nH to 21 nH loop range and show that overshoot scales almost linearly with loop inductance until the sink impedance of the driver dominates. A practical layout rule is derived, together with the measurement fixture needed to verify it without disturbing the loop under test.