Measuring the power consumed by i.MX application processor in a system does not necessarily require fancy, multi-thousand dollar tools. This article details a four-channel power measurement tool can be hand-built in your lab for a fraction of the cost of a commercial measurement system. While it may not be as fast or as accurate as a commercial system, it’s a very useful tool that can be easily built and used to measure run, idle and low power mode power consumption.
At the heart of this measurement system are a pair of shunt resistors for each rail measure current via a sense amplifiers. One shunt is used for the high current range and the other for the low range. The ADCs of a Kinetis microcontroller measure the sense amp outputs and the rail voltages (that’s how we get power), with GPIO controlling FETs that perform the range switching for each rail. The measurement data is collected with a PC using a USB virtual COM port.
The article (here) contains the theory of operation, and assembly and instrumentation tips. Basic source code that controls range switching and makes the measurements is included. In addition to the schematics, layout and bill of materials, links are provided for ordering the low cost PCBs.