Datasheet

UG-186 Evaluation Board User Guide
Rev. 0 | Page 6 of 12
GROUND AND BIAS CURRENT MEASUREMENTS
VOLTAGE SOURCE
VOLTAGE SOURCE
VOLTMETER
1.99711
VOLTMETER
1.99711
VOLTMETER
1.99711
AMMETE R
AMMETER
LOAD LOAD LOAD
0.00112
09299-107
Figure 7. Ground and Bias Current Measurements Setup
Figure 7 shows how the evaluation board can be connected
to a voltage source and ammeters for ground and bias current
measurements. A resistor can be used as the load for the regula-
tor. Ensure that the resistor has a power rating adequate to
handle the power expected to be dissipated across it. An electronic
load can 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 to a voltage source and
ammeters:
1. Insert R1, R2, R3, R4, R5, and R6 to set voltages for an
ADP323. If an ADP322 is used, short R1, R3, and R5
to connect the output voltages to the feedback input for
each LDO.
2. Insert Jumpers JP1, JP2, and JP3 for automatic startup.
3. Connect the positive terminal (+) of the main voltage
source to the VIN and VIN3 pads of the evaluation board.
4. Connect the negative terminal (−) of an ammeter to the
VBIAS pad of the evaluation board.
5. Connect the positive terminal (+) of the bias voltage source
to the positive terminal (+) of the ammeter connected to
the VBIAS pad. Set the bias voltage supply to a voltage
between 2.5 V and 5.5 V.
6. Connect the positive terminal (+) of the other ammeter to
one of the GND pads of the evaluation board.
7. Connect the negative terminal (−) of the ammeter con-
nected to GND to the negative (−) terminal of the main
voltage source.
8. Connect a load between VOUT1, VOUT2, and/or VOUT3
and the negative (−) terminal of the main voltage source.
The voltage sources can now be turned on.
GROUND CURRENT MEASUREMENT
Ground current measurements can determine how much current
the internal circuits of the regulator consume while the circuits
perform the regulation function. To be efficient, the regulator
must consume as little current as possible. Typically, the regulator
uses the maximum current when supplying its largest load level
(200 mA per output). Figure 8 shows the typical ground current
consumption for various load levels as a function of the input
voltage for all three outputs set to 1.2 V and loaded equally.
The ground current for the ADP323 also includes the current
through the output voltage setting dividers, R1 and R2, R3 and
R4, and R5 and R6.