Measure VBAT, VBUS, and VOUT using an oscilloscope

Measure the current with an oscilloscope by probing the voltage drop across a current-measurement resistor.

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 measurements with an oscilloscope shows the VBAT current-measurement case with probe points across the IBAT resistor between pins 1 and 2 on P1.
3. Plot the voltage drop measured across the probe points and calculate the current.
   The measured voltage drop across the resistor is proportional to the current. For instance, a 100 mΩ resistor causes a 0.1 mV drop for each 1 mA drawn by the current being measured.

The current can be averaged or integrated to analyze current and energy consumption over a period. A minimum of one sample every 5 µs is needed to accurately measure the average current.

Figure 1. Current measurements with an oscilloscope

To reduce noise, do the following.

• Use X1 passive probes (no attenuation).
• Enable averaging mode to reduce random noise.
• Enable high-resolution function if available.
• Use an active differential probe across the resistor.