Measure VBAT, VEXT, and VOUT using an oscilloscope

Perform the following steps to measure the current using an oscilloscope.

1. Set the oscilloscope to differential mode or a mode that is similar.
2. Connect the oscilloscope using two probes across the probe points of interest depending on the measurement case.
   Current measurement with an oscilloscope shows the VBAT current-measurement case with probe points across the IBAT resistor between pins 2 and 3 on P6.
3. Calculate or plot the instantaneous current from the voltage drop across the IBAT resistor by taking the difference of the voltages measured on the two probes.
   The voltage drop is proportional to the current. For instance, a 100 mΩ resistor causes a 0.1 mV drop for each 1 mA drawn by the circuit being measured.

The plotted voltage drop can be used to calculate the current at a given point in time. The current can then be averaged or integrated to analyze current and energy consumption over a period.

Figure 1. Current measurement with an oscilloscope

To reduce noise, do the following:

• Use probes with 1x attenuation.
• Enable averaging mode to reduce random noise.
• Enable high-resolution function if it is available.

Use a minimum of 200 kSa/s (one sample every 5 µs) to get the correct average current measurement.