EVAL-ADP220/ADP221
Rev. 0 | Page 5 of 8
LINE REGULATION
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 2.5 V, whichever is greater) and V
INMAX
. For example, for
an ADP220/ADP221 with fixed 2.8 V output, V
IN
needs to
be varied between 3.3 V and 5.5 V. This measurement can
be repeated under different load conditions. Figure 4 shows
the typical line regulation performance of an ADP220/ADP221
with fixed 2.8 V output.
3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
INPUT VOLTAGE (V)
V
OUT
= 2.8V
T
A
= 25°C
LOAD = 10µA
LOAD = 100µA
LOAD = 1mA
LOAD = 10mA
LOAD = 100mA
LOAD = 200mA
2.85
2.83
2.81
2.79
2.77
OUTPUT VOLTAGE (V)
2.75
07575-006
Figure 4. Output Voltage vs. Input Voltage
LOAD REGULATION
For load regulation measurements, the regulator’s outputs are
monitored while the loads are varied. For good load regulation,
the outputs must change as little as possible with varying loads.
The input voltage must be held constant during this measure-
ment. The load currents can be varied from 0 mA to 200 mA
per output. Figure 5 shows the typical load regulation perfor-
mance of a single 2.8 V output of the ADP220/ADP221 for an
input voltage of 3.3 V.
2.85
2.83
2.81
2.79
2.77
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
2.75
0.01 0.1 1 10 100 1k
V
OUT
= 2.8V
V
IN
= 3.3V
T
A
= 25°C
07575-005
Figure 5. Output Voltage vs. Load Current
DROPOUT VOLTAGE
Dropout voltage can be measured using the configuration
shown in Figure 3. Dropout voltage is defined as the input-to-
output voltage differential when the input voltage is set to the
nominal output voltage. This applies only for output voltages
above 2.5 V. Dropout voltage increases with larger loads. For
more accurate measurements, a second voltmeter can be used
to monitor the input voltage across the input capacitor. The
input supply voltage may need to be adjusted to account for IR
drops, especially if large load currents are used. Figure 6 shows
the typical curve of the dropout voltage measurement with
different load currents.
1 10 100 1k
LOAD CURRENT (mA)
250
200
150
100
50
DROPOUT VOLTAGE (mV)
0
2.5V
2.8V
3.3V
07575-014
Figure 6. Dropout Voltage vs. Load Current, V
OUT
= 2.8 V
