Datasheet

Evaluation Board User Guide UG-056
Rev. B | Page 7 of 12
LINE REGULATION MEASUREMENTS
For line regulation measurements, the output of the regulator
is monitored while its input is varied. For good line regulation,
the output 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
+ 0.3 V
(or 2.3 V, whichever is greater) and V
INMAX
.
For example, for the ADP124 with a fixed 3.3 V output, V
IN
must be varied between 3.6 V and 5.5 V. This measurement
can be repeated under different load conditions. Figure 10
shows the typical line regulation performance of the ADP124
with a fixed 3.3 V output.
3.292
3.294
3.296
3.298
3.300
3.302
3.304
3.306
3.308
3.310
3.50 4.00 4.50 5.00 5.50
V
IN
(V)
V
OUT
(V)
I
OUT
= 100µA
I
OUT
= 1mA
I
OUT
= 10mA
I
OUT
= 100mA
I
OUT
= 300mA
I
OUT
= 500mA
08525-007
Figure 10. Output Voltage (V
OUT
) vs. Input Voltage (V
IN
) at T
A
= 25°C
LOAD REGULATION MEASUREMENTS
For load regulation measurements, the output of the regulator
is monitored while the load is varied. For good load regulation,
the output must change as little as possible with varying load.
The input voltage must be held constant during this measure-
ment. The load current can be varied from 0 mA to 500 mA.
Figure 11 shows the typical load regulation performance of the
ADP124 with a fixed 3.3 V output for an input voltage of 3.6 V.
3.303
3.304
3.305
3.306
3.307
3.308
3.309
0.1 1 10 100 1000
I
OUT
(mA)
V
OUT
(V)
08525-008
Figure 11. Output Voltage (V
OUT
) vs. Load Current (I
OUT
) at V
IN
= 3.6 V, V
OUT
=
3.3 V, T
A
= 25°C
DROPOUT VOLTAGE MEASUREMENTS
Dropout voltage can be measured using the configurations
shown in Figure 7, Figure 8, and Figure 9. 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 to output voltages above 2.3 V. Dropout voltage increases
with larger loads.
For more accurate measurements, a second voltage meter 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 12
shows the typical curve of dropout voltage measurements with
different load currents.
0
20
40
60
80
100
120
1 10 100 1000
I
OUT
(mA)
DROPOUT (mV)
08525-009
Figure 12. Dropout Voltage vs. Load Current (I
OUT
) at V
OUT
= 3.3 V, T
A
= 25°C