Datasheet

UG-310 Evaluation Board User Guide
Rev. 0 | Page 4 of 12
Turning On the Evaluation Board
When the power source and load are connected to the evaluation
board, it can be powered for operation.
Perform the following steps to turn on the board:
1. Ensure that the power source voltage is >4.5 V and <20 V.
2. Ensure that EN1 and EN2 are high and monitor the output
voltage.
3. Turn on the load, check that it is drawing the proper load
current, and verify that the output voltage maintains its
regulation.
MEASURING EVALUATION BOARD PERFORMANCE
Measuring the Switching Waveform
To observe the switching waveform with an oscilloscope, place the
oscilloscope probe tip at Test Point J6 (SW1) and J21 (SW2) with
the probe ground at GND. Set the scope to dc with the appropriate
voltage and time divisions. The switching waveform limits should
alternate approximately between 0 V and the input voltage.
Measuring Load Regulation
Load regulation can be tested by observing the change in the
output voltage with increasing output load current. To minimize
the voltage drop, use short low resistance wires.
Measuring Line Regulation
Vary the input voltage and examine the change in the output
voltage with a fixed output current.
Line Transient Response
Generate a step input voltage change and observe the behavior
of the output voltage using an oscilloscope.
Load Transient Response
Generate a load current transient at the output and observe the
output voltage response using an oscilloscope. Attach the current
probe to the wire between the output and the load to capture
the current transient waveform.
Measuring Efficiency
The efficiency, η, is measured by comparing the input power with
the output power.
ININ
OUTOUT
IV
IV
η
×
×
=
Measure the input and output voltages as close as possible to the
input and output capacitors to reduce the effect of voltage drop.
Measuring Inductor Current
The inductor current can be measured by removing one end of
the inductor from its pad and connecting a current loop in series.
A current probe can be connected onto this wire.
Measuring Output Voltage Ripple
To observe the output voltage ripple, place the oscilloscope probe
across the output capacitor with the probe ground lead connected
to the negative (−) capacitor terminal and the probe tip placed at
the positive (+) capacitor terminal. Set the oscilloscope to ac,
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 an easy way to measure the output ripple properly.
It requires removing the oscilloscope probe sheath and wrapping
an unshielded wire around the oscilloscope probe. By keeping
the ground length of the oscilloscope probe as short as possible,
the true ripple can be measured.
10113-002
Figure 2. Measuring Output Voltage Ripple
MODIFYING THE BOARD
To mo dif y the ADP2323 evaluation board configuration, unsolder
and/or replace/remove the appropriate passive components or
jumpers on the board.
Changing the Output Voltages
The output voltage setpoints of the ADP2323 can be changed by
replacing the R4, R7, R18, and R17 resistors with the resistor values
shown in Table 2.
Table 2. Resistive Divider for Various Output Voltages
V
OUT
(V) R4/R18, ±1% (kΩ) R7/R17, ±1% (kΩ)
1.0 10 15
1.2 10 10
1.5 15 10
1.8 20 10
2.5 47.5 15
3.3 10 2.21
5.0 22 3
To limit output voltage accuracy degradation due to the FBx pin
bias current (0.1 μA maximum) to less than 0.5% (maximum),
ensure that the bottom divider string resistor, R7 (R17 for
Channel 2), is less than 30 kΩ.