7 Low Noise and Controlling EMI

In switching power supplies, electromagnetic interference (EMI) noise is unavoidable due to the switching actions of the semiconductor devices and resulting discontinuous currents. EMI control is one of the more difficult challenges in switching power supplies design. This section defines and discusses electromagnetic interference and describes ways to mitigate its effects.

Not All Jitter is Created Equal:SLUA747

This application report offers a tutorial discussion on jitter in switching DC-DC converters. Not all power supply designs are equally susceptible to jitter, nor are they equally affected by jitter. Modes of switching jitter are defined and explained for several popular control architectures, which are then analyzed for sources of jitter.

Controlling the Switch-node Ringing of Synchronous Buck Converters:SLYT465

This article focuses on three circuit designs that control switch-node ringing with either a boot resistor, a high-side gate resistor, or a snubber. Data is presented for each approach, and the benefits of each are also discussed.

Simplify Low-EMI Design with Power Modules:SLYY123

This paper explains the sources of EMI in a switching power supply and methods or technologies for mitigating EMI. I will also show you how power modules (controller, high side and low side FET and inductor in one package) help reduce EMI.

Snubber Circuits: Theory, Design and Application:SLUP100

This article describes some of the various types of snubbers, where they are used, how they function, how they are designed and what their limitations are.

Minimizing Output Ripple During Startup:SLVA866

This application note uses the TPS54620 as an example to provide recommendations to reduce the ripple caused by pulse-skipping during startup and shows some newer parts which use different circuits during startup to reduce the output voltage ripple.

Measuring Various Types of Low-frequency Noise from DC/DC Switching Converters:SLYY134

This white paper explains sources of low-frequency noise in bipolar junction transistors (BJTs), metal-oxide semiconductor field-effect transistors (MOSFETs) and resistors, and how this noise propagates to the output voltage of a DC/DC converter.

Using a 4MHz switching regulator w/o a Linear Regulator to Power a Data Converter:SLYT756

This article shows how a high-frequency DC/DC converter offers low ripple noise and good power-supply ripple rejection compared to a 400-kHz DC/DC converter followed by an LDO.

Extend Battery Life with < 100 nA IQ Buck Converter Achieving < 150 µV Voltage Ripple (with PI filter design):SLVAEG1

This document discusses different architectures for implementing buck converters for a battery-powered application, and the trade-offs for each.

Analysis and Design of Input Filters for DC-DC Circuits:SNVA801

This application report analyzes the influence of the input filter on the DC-DC control loop transfer function, and the influence of a closed loop on the input filter, explains why input filter causes unexpected problem, and suggests how to eliminate the side effect of the input filter.

Calculating Output Capacitance to Meet Transient and Ripple Requirements of an Integrated POL Converter Design Based on D-CAPx™ Modulators:SLVA874

This document provides guidance on how to calculate the amount of output capacitance needed to meet the transient and ripple requirements of a general buck converter design. D-CAPx modulators are used in the example.

Controlling Output Ripple and Achieving ESR Independence with Constant On-Time Regulators:SNVA166

Of all the voltage regulator control strategies ever devised, the hysteretic regulator is probably about the simplest. This control methodology simply turns a switch on when the output voltage is below a reference and turns the switch off when the output rises to a slightly higher reference. The output ripple is therefore a direct function of the difference between the upper and lower reference threshold, the hysteresis amplitude. It’s hard to imagine something much simpler and, as usual, with simplicity comes performance shortcoming.

EMI/RFI Board Design:SNLA016

This generic application note defines electromagnetic interference and describes how it relates to the performance of a system. It looks at examples of inter-system noise and intra-system noise and presents techniques that can be used to ensure electromagnetic compatibility throughout a system and between systems.

Simple Success With Conducted EMI From DC/DC Converters:SNVA489

This paper details conducted EMI characteristics and mitigation techniques in switching power supplies.

Layout Tips for EMI Reduction in DC/DC Converters:SNVA638

This application note explores how the layout of your DC/DC power supply can significantly affect the amount of EMI that it produces. It will discuss several variations of a layout, analyze the results, and provide answers to some common EMI questions.

Output Noise Filtering for DC/DC Power Modules:SNVA871

This application report provides a comparative analysis between a LDO and a second stage LC filter to minimize the output of the LMZM33606 power module.

Designing High-Performance, Low-EMI Automotive Power Supplies:SNVA780

This application report discusses the unique challenges to designing automotive power supplies.

Enhanced HotRod QFN Package: Achieving Low EMI Performance in Industry’s Smallest 4-A Converter:SNVA935

This application report highlights TI’s fist DC/DC converter with Enhanced HotRod QFN package technology and provides insight on the EMI and thermal performance of the LM60440 device.

Improve High-Current DC/DC Regulator EMI Performance for Free With Optimized Power Stage Layout:SNVA803

This Tech Note explores EMI abatement in high-current DC/DC regulator circuits that employ a controller paired with discrete high-side and low-side silicon power MOSFETs. Using a single-sided PCB layout that specifically minimizes the parasitic inductance of the switching power loop, the switch-node voltage overshoot and ringing during MOSFET commutation are reduced, thus lowering regulator EMI signature.