EVAL-ADP7158 Datasheet, PDF (5/8 Pages) Analog Devices – Evaluating the ADP7158 Ultralow Noise

EVAL-ADP7158 User Guide
LINE REGULATION MEASUREMENTS
For line regulation measurements, the change in the output of
the regulator is measured when the input is varied. For good
line regulation, the output must maintain a minimal change in
voltage with respect to varying input voltage levels. To ensure
the device is not in dropout mode during this measurement, vary
VIN between VOUT_NOM + 0.5 V (or 2.3 V, whichever is greater) and
VIN_MAX. For example, if the ADP7158 has a fixed 3.3 V output,
vary VIN between 3.8 V and 5.5 V. This measurement can be
repeated under different load conditions. The typical line
regulation performance of an ADP7158 with a fixed 3.3 V
output is shown in Figure 4.
3.35
3.34
3.33
3.32
3.31
3.30
I_LOAD = 10mA
I_LOAD = 100mA
I_LOAD = 600mA
I_LOAD = 1200mA
I_LOAD = 2000mA
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 4. 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 monitored while the load current is varied. For a
good load regulation, the output must maintain a minimal
voltage change with respect to varying load current levels. Hold
the input voltage constant during this measurement. The load
current can vary from 0 mA to 2 A. The typical load regulation
performance of an ADP7158 with a fixed 3.3 V output for an
input voltage of 3.8 V is shown in Figure 5.
UG-794
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 5. 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 diff-
erential 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 increases with larger loads. Figure 3 shows the
configuration for measuring dropout voltage.
For more accurate measurements, use a second voltmeter to
monitor the input voltage across the input capacitor. The input
supply voltage may require adjusting for voltage drops, especially if
using large load currents. The typical curve of dropout voltage
measurements over varying load current levels is shown in
Figure 6.
0.25
0.20
0.15
0.10
0.05
0
10m
100
1
10
I_LOAD (A)
Figure 6. Dropout Voltage vs. Load Current (ILOAD), VOUT = 3.3 V, TA = 25°C,
CIN = COUT = 10 µF
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