UG-880
ADP5302-EVALZ User Guide
Rev. 0 | Page 4 of 7
MEASURING EVALUATION BOARD PERFORMANCE
Measuring the Switching Waveform
To observe the switching waveform with an oscilloscope, place
the oscilloscope probe tip at the TP2 and TP5 test points with the
probe ground connected to GND. Set the oscilloscope to a dc
coupling, 2 V/division, 1 µs/division time base. The switching
waveform alternates between 0 V and the approximate input
voltage.
Measuring Load Regulation
Test load regulation by increasing the load at the output and
measuring the output voltage between the TP4 and TP7 test
points.
Measuring Line Regulation
Vary the input voltage and measure the output voltage at a fixed
output current. The input voltage can be measured between the
TP1 and TP5 test points. The output voltage is measured
between the TP4 and TP7 test points.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power
with the output power.
IN
IN
OUT
OUT
I
V
I
V
η
×
×
=
Measuring Inductor Current
Measure the inductor current by removing one end of the
inductor from the pad on the board and using a wire connected
between the pad and the inductor. A current probe can then be
used to measure the inductor current.
Measuring Output Voltage Ripple
To observe the output voltage ripple, place an oscilloscope
probe across Output Capacitors C1, C8, and C10 with the probe
ground lead placed at the negative capacitor terminal (−) and
the probe tip placed at the positive capacitor terminal (+). Set
the oscilloscope to an ac coupling, 10 mV/division,
2 µs/division time base and 20 MHz bandwidth.
A standard oscilloscope probe has a long wire ground clip. For
high frequency measurements, this ground clip picks up high
frequency noise and injects it into the measured output ripple.
Figure 2 shows a simple way to properly measure the output
ripple. It requires removing the oscilloscope probe sheath and
wrapping a nonshielded wire around the oscilloscope probe.
By keeping the ground lengths of the oscilloscope probe as
short as possible, true ripple can be measured.
Figure 2. Output Ripple Measurement
Output Voltage Change
The output voltage of the evaluation board is preset to 1.8 V.
However, the output voltage can be adjusted with an external
VID resistor (see the
ADP5302
data sheet).
13506-
002
