Reducing Noise Generated By Switching Regulators

by Frederik Dostal, Analog Devices, Munich, Germany, How2Power Today, Dec 17 2015

Focus:
In many applications noise generated by switched-mode power supplies (SMPSs) needs to be limited so that analog data integrity is not compromised and also to pass certain EMI requirements. This article will introduce the different types of SMPS noise, discuss different noise-coupling mechanisms and ultimately present solutions to reduce the generation of noise and to filter remaining disturbances. Noise sources discussed include switching frequency noise, high-frequency noise produced by switching transitions, ringing after switching transitions, ringing in discontinuous conduction mode (DCM) and beat frequencies caused by multiple switching regulators in one system. Noise reduction techniques discussed include PCB layout, component placement, grounding methods, use of snubbers and clamps, use of CCM rather than DCM operation, synchronization of switching frequencies, and input filtering. While the concepts discussed are generally applicable to all SMPS designs, the focus here is mainly on nonisolated, dc-dc converters or point-of-load converters (POLs).

What you’ll learn:

• How to understand the various sources of noise produced by switching regulators
• How to alleviate switching regulator noise

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