Evaluation Board User Guide UG-412
Rev. 0 | Page 5 of 8
Figure 5 and Figure 6 show how the evaluation board can be
connected to a voltage source and a voltmeter for basic output
voltage accuracy measurements. A resistor can be used as the
load for the regulator. Ensure that the resistor has a power
rating that is adequate for handling the power expected to be
dissipated across it. An electronic load can also be used as an
alternative. Ensure that the voltage source can supply enough
current for the expected load levels.
Use the following steps to connect the evaluation board to a
voltage source and voltmeter:
1. Connect the positive terminal (+) of the voltage source to
one of the GND pads on the evaluation board.
2. Connect the negative terminal (−) of the voltage source to
the VIN pad of the evaluation board.
3. Connect a load between the VOUT pad and one of the
GND pads.
4. Connect the positive terminal (+) of the voltmeter to one
of the GND pads.
5. Connect the negative terminal (−) of the voltmeter to the
VOUT pad.
The voltage source can then be turned on. If LK1 is inserted
(connecting EN to VIN for automatic startup), the regulator
powers up.
If the load current is large, connect the voltmeter as close as
possible to the output capacitor to reduce the effects of IR drops.
LINE REGULATION
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 during this
measurement, V
IN
must be varied between V
OUTNOM
− 1 V (or
−2.7 V, whichever is greater) and V
INMAX
. For example, for an
adjustable ADP7182 set to −15 V, V
IN
must be varied between
−16 V and −28 V. This measurement can be repeated under
different load conditions. Figure 7 shows the typical line
regulation performance of an ADP7182 with a −15 V output.
–30 –25 –20 –15
V
OUT
(V)
V
IN
(V)
–15.30
–15.25
–15.20
–15.15
–15.10
–15.05
–15.00
–14.95
–14.90
–14.85
–14.80
LOAD = 100µA
LOAD = 1mA
LOAD = 10mA
LOAD = 50mA
LOAD = 100mA
LOAD = 200mA
10708-007
Figure 7. Output Voltage vs. Input Voltage
LOAD REGULATION
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 measurement. The
load current can be varied from 0 mA to −200 mA. Figure 8 shows
the typical load regulation performance of an ADP7182 with a
−15 V output for an input voltage of −16 V.
–200 –150 –100 –50 0
V
OUT
(V)
I
LOAD
(mA)
–15.30
–15.25
–15.20
–15.15
–15.10
–15.05
–15.00
–14.95
–14.90
–14.85
–14.80
10708-008
Figure 8. Output Voltage vs. Load Current
DROPOUT VOLTAGE
The dropout voltage can be measured using the configurations
shown in Figure 5 and Figure 6. The 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 less than −3 V. The dropout voltage increases with
larger loads. For more accurate measurements, use a second
voltmeter 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 9
shows a typical curve of dropout voltage measurements with
different load currents.
1 10 100 1000
DROPOUT VOLTAGE (mV)
I
LOAD
(mA)
–140
–120
–100
–80
–60
–40
–20
0
10708-009
Figure 9. Dropout Voltage vs. Load Current
