Datasheet

Evaluation Board User Guide UG-300
Rev. A | Page 3 of 8
EVALUATION BOARD OVERVIEW
The ADP2126 evaluation board is fully assembled and tested.
The following sections describe the various connectors on the
board, the proper evaluation setup, and the testing capabilities
of the evaluation board.
INPUT/OUTPUT CONNECTORS
MODE Jumper
The MODE connector controls the operating mode of the
ADP2126. Use a jumper to connect the center pin to GND or
VIN. Alternatively, connect to the center pin and control the
MODE pin directly with an external device. See the specifications
section in the ADP2126 data sheet for the high and low threshold
voltage levels. Do not leave the MODE pin floating.
EXTCLK Test Point
This test point is used to enable or disable the converter. Connect
the EXTCLK pin to GND to disable the converter. Apply a 6 MHz
to 27 MHz clock signal or a logic high signal to the EXTCLK pin
to enable the converter. See the specifications section in the
ADP2126 data sheet for the high and low threshold voltage
levels. Do not leave the EXTCLK pin floating.
VOUT Test Bus
The VOUT test bus provides access to the regulated output voltage
and the FB (feedback) pin of the part. A load of up to 500 mA
can be applied to this bus.
VIN Test Bus
The VIN test bus connects the positive input supply voltage to
the VIN pin. Connect the power supply to this bus and keep the
wires as short as possible to minimize the EMI transmission.
GND Test Bus
The GND test bus is the ground connection for the part and the
external components via the GND pin. Attach ground connections
from external equipment to this bus.
SW Test Point
The SW test point allows access to the switch node (SW pin) of
the ADP2126 to monitor the switching behavior. An LC filter is
connected to this pin on the board. Connect a BNC cable to
measure the switching frequency to this test point.
The ADP2126 incorporates spread spectrum via a controlled
variance of the switching frequency over a wider band of
frequencies. This distribution of the frequency content spreads
the spectral density over a wider bandwidth, resulting in lower
peak emission levels.
EVALUATION SETUP
Follow these setup instructions to ensure proper operation of
the ADP2126 evaluation board:
1. Connect the input supply ground to GND.
2. Connect the positive input supply to VIN.
3. Connect the desired load between VOUT and PGND. The
ADP2126 can supply up to 500 mA.
4. Connect the EXTCLK pin to GND to disable the converter,
or apply a 6 MHz to 27 MHz clock signal or a logic high
signal to the EXTCLK pin to enable the converter.
5. Apply an input voltage between 2.1 V and 5.5 V (6.0 V
absolute maximum.)
PERFORMANCE EVALUATION
Typical performance characteristic graphs and oscilloscope
waveforms are provided in the ADP2126 data sheet.
Output Accuracy
The output accuracy is verified by monitoring the output voltage at
VOUT while testing both the line and load regulation.
Line Regulation
The line regulation is observed and measured by monitoring
the output voltage at VOUT while varying the input voltage
applied to the VIN test bus.
Load Regulation
The load regulation is observed and measured by monitoring the
output voltage at VOUT while sweeping the applied load between
VOUT and GND. To minimize voltage drop, use short low
resistance wires, especially for heavy loads.
Efficiency
The efficiency, η, is calculated by comparing the input power to
the output power.
ININ
OUTOUT
IV
I
V
η
×
×
=
Output Voltage Ripple
The output voltage ripple is visible by placing an oscilloscope
across the output capacitor (COUT). Set the oscilloscope to ac
coupling or apply a dc offset for proper resolution.
Line Transient
Generate a high speed transient in the voltage applied to VIN and
observe the behavior of the evaluation board at the SW test
point and the VOUT test bus. To see the most accurate line
transient waveform, place a probe directly on the output capacitor
terminal with a short path to ground to limit noise and stray
inductance.