Datasheet

UG-329 Evaluation Board User Guide
Rev. 0 | Page 4 of 8
MEASURING EVALUATION BOARD PERFORMANCE
Measuring the Switching Waveform
To observe the switching waveform with an oscilloscope, place
the oscilloscope probe tip at Test Point T4 with the probe ground
connected to GND. Set the oscilloscope to a dc coupling, 2 V/divi-
sion, 1 µs/division time base. The switching waveform should
alternate between 0 V and the approximate input voltage.
Measuring Load Regulation
Load regulation should be tested by increasing the load at the
output and measuring the output voltage between the T3 and
T5 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
T1 and T2 test points. The output voltage is measured between
the T3 and T5 test points.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power
with the output power.
ININ
OUTOUT
IV
IV
η
×
×
=
Measuring Inductor Current
The inductor current can be measured by removing one end of
the inductor from the pad on the board and connecting a wire
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 Capacitor C4 with the probe ground lead
placed at the negative capacitor terminal (−) and the probe tip
placed at the positive capacitor terminal (+). Set the oscillo-
scope 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 length of the oscilloscope probe as short as
possible, true ripple can be measured.
10236-002
Figure 2. Output Ripple Measurement
Output Voltage Change
The output voltage of the ADP2164 evaluation board is preset
to 1.2 V. However, the output voltage can be adjusted using the
following equation:








+
×=
R3
R3R4
V
OUT
V6.0