Datasheet

UG-186 Evaluation Board User Guide
Rev. 0 | Page 4 of 12
OUTPUT VOLTAGE MEASUREMENTS
VOLTAGE SOURCE
VOLTMETER
VOLTAGE SOURCE
VOLTMETER VOLTMETER
LOAD
LOAD LOAD
VOLTMETER
1.99711
1.99711 1.99711
1.99711
09299-003
Figure 3. Output Voltage Measurement Setup
Figure 3 shows how the evaluation board can be connected to a
voltage source and voltmeters for basic output voltage accuracy
measurements. A resistor can be used as the load for the regula-
tor. Ensure that the resistor has a power rating adequate to handle
the power expected to be dissipated across it. An electronic load
can be used as an alternative. In addition, ensure that the voltage
source can supply enough current for the expected load levels.
Follow these steps to connect to a voltage source and voltmeters:
1. Insert R1, R2, R3, R4, R5, and R6 to set voltages for an
ADP323. If an ADP322 is used, short R1, R3, and R5
to connect the output voltages to the feedback input for
each LDO.
2. Insert Jumpers JP1, JP2, and JP3 for automatic startup.
3. Connect the negative terminal (−) of the voltage sources to
one of the GND pads on the evaluation board.
4. Connect the positive terminal (+) of the main voltage
source to the VIN and VIN3 pads of the evaluation board.
5. Connect the positive terminal (+) of the bias voltage source
to the VBIAS pad of the evaluation board. Set the bias
voltage supply to a voltage from 2.5 V to 5.5 V.
6. Connect a load between VOUT1, VOUT2, and/or VOUT3
and one of the GND pads.
7. Connect the negative terminal (−) of the voltmeters to one
of the GND pads.
8. Connect the positive terminal (+) of the voltmeters to
VOUT1, VOUT2, and/or VOUT3 and VIN/VIN3.
The voltage sources can now be turned on.
LINE REGULATION MEASUREMENTS
For line regulation measurements, the regulator’s outputs are
monitored while its input is varied. For good line regulation,
the outputs must change as little as possible with varying input
levels. To ensure that the device is not in dropout mode during
this measurement, V
IN
must be varied between V
OUTNOM
+ 0.5 V
(or 1.8 V, whichever is greater) and V
INMAX
, where V
OUTNOM
is the
highest of the three output voltages. For example, for an ADP322/
ADP323 with a fixed 1.8 V output, V
IN
must be varied between
2.3 V and 5.5 V. This measurement can be repeated under different
load conditions. Figure 4 shows the typical line regulation perfor-
mance of the ADP322/ADP323 with a fixed 1.8 V output.