Troubleshooting Distributed Power Systems (Part 5): Using Current Injectors

Focus:

Previous videos in this series discussed the use of vector network analyzers (VNAs) to measure impedance using one- or two-port configurations. This video discusses another method of measuring impedance—the current injector method. Although not quite as accurate as the two-port VNA impedance measurement, the current injection technique has advantages including wide range (approx. 1 milliohm to thousands of ohms), the ability to measure in-system, and a suitability for measuring low-power devices such as op amps, voltage references, and voltage regulators. In addition, current injectors can be used to carry out other types of tests such as non-invasively measuring PSRR, determining power integrity and signal integrity sensitivity, and in generating high-speed load steps. In this video, Steve Sandler discusses each of these current injector measurement capabilities and presents test examples that illustrate how designers can perform and interpret these measurements. Along the way, Sandler offers many test tips to help the engineer obtain the most accurate results.

What you’ll learn:

• How to understand the pros and cons of using current injectors in combination with VNAs to measure the impedance of power circuits
• How to measure PSRR noninvasively or to generate high-speed mload steps using current injectors
• How to test a system’s power integrity sensitivity by using a current injector to apply noise to a power bus and then measuring the phase noise on the system’s clock

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Author & Publication:

Steve Sandler, AEi Systems and Picotest, Phoenix, Ariz, How2Power Today, Oct 15 2013

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