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The power consumption specifications in the data sheet of a chip are not always the best representation of real-life application. This application note tries to explain the setup and typical conditions under which the measurements are taken for the JIBEPOS reference design. At the end, the results are presented in graphical form.
To measure the current on different supply lines (1.0V, 1.8V, and 3.3V), the on-board power supply is removed and each power-rail is fed directly by Tektronix PWS2721 DC power supplies. The current measurement is completed on the Tektronix DMM4040 6½ Digital Precision Multimeter. These multimeters have the ability to log the current over a period of time.
Test setup is shown in Figure 1.
Figure 1. Test setup.
Let the JIBEPOS power up normally. As it goes through different sequences such as loading the u-boot to internal memory, loading the kernel to external LPDDR, and booting the kernel from there, the current consumption is logged during each operation. Besides the booting sequence, we implement two different use cases:
This data is presented in Figure 2. The different operations are clearly marked in this figure.
Figure 2. Current profile for different operations per supply rail.
The breakdown of the average power consumptions for each operation per supply rail is presented in Table 1.
Table 1. Current and Power Consumption per Rail Voltage and per Operation
|Current Consumption on Each Voltage Rail (mA)|
|RAIL VOLTAGE||1.0V||1.8V||3.3V||Total Power for Each Operation (mW)|
|Operation||ROM Loading U-Boot||328.0||1.3||126.0||746|
|U-Boot Loading Kernel||422.0||30.8||147.0||961|
|Zip and Unzip Operations||421.0||39.5||109.0||852|
Also in Figure 3, Figure 4, and Figure 5, the histograms of the current consumption are presented for each voltage rail.
Figure 3. 1V rail current histogram.
Figure 4. 1.8V rail current histogram.
Figure 5. 3.3V rail current histogram.