EVAL-ADP7159 Datasheet, PDF (6/9 Pages) Analog Devices – Power supply rejection ratio

UG-811
LINE REGULATION MEASUREMENTS
For line regulation measurements, the change in the output of
the regulator is measured when the inputis varied. For good
line regulation, the output must maintain a minimal change in
voltage with respect to varying input voltage levels. To ensure
that the device is not in dropout mode during this
measurement, vary VIN between VIN_MIN and V . IN_MAX See Table 2
for selection guides. For example, forthe ADP7159-04, VIN can
vary from 3.8 V to 5.5 V. This measurement can be repeated
under different load conditions. The typical line regulation
performance of an ADP7159 with a 3.3 V output is shown in
Figure 7.
3.35
3.34
3.33
3.32
I_LOAD = 0mA
I_LOAD = 10mA
I_LOAD = 100mA
I_LOAD = 600mA
I_LOAD = 1200mA
I_LOAD = 2000mA
3.31
3.30
3.29
3.28
3.27
3.26
3.25
3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6
V_IN (V)
Figure 7. Output Voltage(VOUT) vs. Input Voltage (VIN), VOUT = 3.3 V, TA = 25°C,
CIN = COUT = 10 µF
LOAD REGULATION MEASUREMENTS
For load regulation measurements, the output voltage of the
regulator is monitoredwhile the load current is varied. Fora good
load regulation, the output must maintain a minimal voltage
change withrespect to varyingload current levels.Holdthe input
voltage constant during this measurement. The load current can
vary from 0 mAto 2 A. The typical load regulationperformance of
an ADP7159 with a 3.3 V output for an input voltage of 3.8 V is
shown in Figure 8.
EVAL-ADP7159 User Guide
3.35
3.34
3.33
3.32
3.31
3.30
3.29
3.28
3.27
3.26
3.25
0.1m
1m
10m
100m
1
10
I_LOAD (A)
Figure 8. Output Voltage (VOUT) vs. Load Current (ILOAD), VOUT = 3.3 V, TA = 25°C,
CIN = COUT = 10 µF
DROPOUT VOLTAGE MEASUREMENTS
Dropout voltage is defined as the input to output voltage
differential when the input voltage is set to the nominal output
voltage. This definition is only applicable to output voltages
above 2.3 V. Dropout voltage increaseswith largerloads. Figure 5
and Figure 6 show the configuration for measuring dropout
voltage.
For more accurate measurements, use a second voltmeterto
monitor the input voltage across the input capacitor. The input
supply voltage mayrequire adjustingfor voltage drops, especially if
using large load currents. The typical curve of dropout voltage
measurements over varying load current levelsis shown in Figure 9.
0.25
0.20
0.15
0.10
0.05
0
10m
100m
1
10
I_LOAD (A)
Figure 9. Dropout Voltage vs. Load Current (ILOAD), VOUT = 3.3 V, TA = 25°C,
CIN = COUT = 10 µF
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