Output Impedance of Power Supplies

In this application note, we show how to measure the output impedance of DC/DC converters or voltage regulators and how to use this information to derive the phase margin and select the right decoupling network.

The output impedance of a voltage regulator or DC/DC converter contains information about the control-loop stability as well as information about the decoupling network. 

The theory behind the Non-Invasive Stability Measurement (NISM) is explaind and verified based on a lab-experiment on a SEPIC converter.

If you want to know more about why measuring the ouptut impedance of a DC/DC converter can support your design process, please check out the following application note:

Appnote: Output Impedance for Stability Analysis

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Related Links

  • TI Seminar TopicCheck out this document from Texas Instruments that deals with "accelerating power-supply compliance to specification". As part of it, some theory on the output impedance of power supplies is explained.

Related Information

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This presentation will cover the basics of dynamic output impedance and PDN (Power Delivery Network) impedance, focusing on measuring low impedance using the Bode 500 in conjunction with Picotest PDN probes.
This webinar starts with the basics of the correlation between output impedance and phase-margin, shows various Output Impedance measurement methods as well as an example on how to improve line-disturbance rejection of an ADC by optimizing the decoupling of the voltage supply.
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