UG-199 Evaluation Board User Guide
Rev. 0 | Page 4 of 8
EVALUATION SETUP
Follow these setup instructions to ensure proper operation of
the ADP2121 evaluation board:
1. Connect the positive input supply to VIN.
2. Connect the input supply ground to PGND.
3. Connect the desired load between VOUT and PGND. For
VIN = 2.3 V to 2.5 V, the maximum load the ADP2121 can
deliver increases linearly from 300 mA to 500 mA. For
VIN = 2.5 V to 2.7 V, the maximum load increases linearly
from 500 mA to 600 mA. Above VIN = 2.7 V, the ADP2121
can supply up to 600 mA.
4. Connect EN to enable or disable the converter and MODE
to select between auto mode and PWM mode.
5. Apply a VIN between 2.3 V and 5.5 V (6.0 V absolute
maximum.)
PERFORMANCE EVALUATION
The resulting oscilloscope waveforms and typical performance
characteristics for the following tests are provided in the
ADP2121 data sheet.
Line Regulation
The line regulation is observed and measured by monitoring
the output voltage at VOUT while varying the input voltage
applied to VIN.
Load Regulation
The load regulation is observed and measured by monitoring
the output voltage at VOUT while sweeping the applied load
between VOUT and PGND. To minimize voltage drop, use
short, low resistance wires, especially for heavy loads.
Output Accuracy
The output accuracy is verified by monitoring the output voltage at
VOUT while testing both the line and load regulation.
Efficiency
The efficiency, η, is calculated by comparing the input power to
the output power.
ININ
OUTOUT
IV
V
×
×
=η
PFM/PWM Transition
To observe the PFM/PWM transition, place the converter in
auto mode. Connect an oscilloscope to the SW test point and
vary the load current applied to VOUT between 70 mA and
170 mA (typical). The PFM/PWM transition point varies with
the input voltage applied to VIN. Hysteresis exists in the load
transition point to prevent oscillation between modes and is
evident in the different values seen for the rising and the falling
load sweeps.
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 load transient
waveform, place a probe directly on the output capacitor terminal
with a short path to ground to limit noise and stray inductance.
Load Transient
Generate a fast transient in the current applied to VOUT and
observe the behavior of the evaluation board at the SW test
point and the VOUT test bus. To see the most accurate load
transient waveform, place a probe directly on the output capacitor
terminal with a short path to ground to limit noise and stray
inductance.
Oscillator Frequency
The oscillator frequency is measured by connecting an oscilloscope
to the SW test point with the converter in PWM mode.
Inductor Current
The inductor current is accessible by removing one side of the
inductor from its pad and connecting a current loop in series.
Place an oscilloscope current probe on the loop to view the
current waveform.
