Dynamic current measurement principle UM2243
26/41 UM2243 Rev 2
10.3 Dynamic current measurements special care
To guarantee the stability of the output voltage stabilization loop (see Figure 17), it is
recommended to insert JP4 jumper to add additional 2.2 µF capacitor on output voltage
VOUT (see
Figure 2 for more details). Otherwise the output voltage stabilization loop might
oscillate, reducing the accuracy of current and power measurements.
Jumper JP4 is not needed if the target board has 1 µF minimum decoupling capacitance at
its input power path. In this case, jumper JP4 can be removed or kept inserted.
This additional 2.2 µF decoupling capacitance has no effect on energy measurements (as
energy measurement is integration of power measurement over time).
Nevertheless, the 2.2 µF decoupling capacitance has some effect on instantaneous current
measurements i(t), as it acts as low-pass filter; the current waveform is smoothed. This
might be possible when performing fast current measurement acquisitions using the
STM32CubeMonitor-Power tool, then zooming into the range of approximately 10 to 100
µs
of measurement samples.
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