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Application Report
SLVA236 – April 2006
Performing Accurate PFM Mode Efficiency Measurements
Jatan Naik ......................................................................................................... PPM - Portable Power
ABSTRACT
When performing measurements on DC-DC converters using pulse frequency
modulation (PFM), proper care must be taken to ensure that the measurements are
accurate. Due to the nature of a converter operating in PFM mode, the test setup
required to obtain correct measurements differs from the test setup that is normally
used to acquire measurements of the device operating in PWM mode. An improper test
setup can result in incorrect efficiency measurement data that varies considerably from
the data-sheet specifications provided by Texas Instruments.
This application report contains guidelines that can assist the user in acquiring accurate
efficiency measurements. An example of measurements taken on the TPS61020 is
provided.
Contents
1 Introduction .......................................................................................... 2
2 Efficiency Measurements .......................................................................... 3
3 Conclusion ........................................................................................... 6
List of Figures
1 PWM Efficiency ..................................................................................... 2
2 Power Save Mode Efficiency ...................................................................... 2
3 PWM Switching Node Waveform ................................................................. 3
4 PFM Switching Node Waveform .................................................................. 3
5 PWM Measurements ............................................................................... 4
6 PFM Measurements ................................................................................ 5
7 Input Current Waveform ........................................................................... 5
8 Efficiency Comparison ............................................................................. 6
SLVA236 – April 2006 Performing Accurate PFM Mode Efficiency Measurements 1
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