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Achieving low noise and low EMI performance with DC/DC switching regulators

Mitigating switching regulator EMI and noise is seen by engineers as a black art. Mess with the feng shui of the PCB layout too much, and the system may not pass CISPR standards. Because of this, many power designers simply turn to linear regulators as a guaranteed way to avoid the headache of reducing emissions. But with inferior efficiency, linear regulators then present potential thermal issues that could be avoided by using a switching regulator. How can you get the best of both worlds?

This training series - along with all of the accompanying documentation - is meant to illustrate how engineers can get the superior efficiency of a switcher while also overcoming the challenges of EMI and noise. Both conceptual and practical examples of EMI and noise best practices are presented, along with specific commentary regarding powering automotive  systems as well as noise-sensitive analog circuitry.

1. Concepts of Switching Regulator EMI and Noise Mitigation

Before we dive into specific application-based examples of noise and EMI mitigation, let's start with the basics. What is noise? What is EMI? What is ripple? How are they measured? What are some common approaches to limiting their effects? This section discusses these topics with a more conceptual approach to serve as a primer for the rest of the series. 

Resources

Blog: How you measure your ripple can make you or break you

Application Note: Switch node ringing measurement and minimization with an RC snubber and bootstrap resistor

Blog: What is a low noise inverting buck converter?

Training: 

# Title Duration
1.1 Understanding EMI and Mitigating Noise in DC/DC Converters
This training delves into EMI in significant detail to provide an understanding from both theoretical and practical standpoints. 
34:51
1.2 LDO or Switcher?...That is the Question
Historically, designers have defaulted to LDOs for specific power conversions. This training explains why the SIMPLE SWITCHER® Nano Module switching power...
24:00
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2. EMI and Noise Mitigation Techniques in Practice

Now that we understand the sources of EMI and noise in switching regulators, and some of the common approaches to mitigating each, let's take a closer look at real-world examples of reducing their effects. In this section we will examine the impacts of various mitigation techniques to help you decide which approach makes the most sense in your design. Techniques covered in this discussion include external component placement, filter options and design, frequency manipulation via spread spectrum or dithering, snubbers, boot resistors, and more.

Resources

Article: Reduce buck-converter EMI and voltage stress by minimizing inductive parasitics

App Note: Simple Success With Conducted EMI From DCDC Converters

TI Design: CISPR-22 EMI-Optimized Reference Design Featuring LMR23630 Synchronous DC/DC Buck Converter

Blog: How to reduce acoustic noise of MLCCs in power applications

Training:

# Title Duration
2.1 Engineer It: How to Achieve Great EMI Performance With a Non-Synchronous Converter
Discover the keys to achieving excellent EMI performance with a non-synchronous buck converter.
10:43
2.2 Layout Tips for Radiated EMI Reduction in Your Designs
Layout tips for good EMI performance, featuring the LM4360x and LM4600x synchronous SIMPLE SWITCHER family of wide Vin regulators
07:13
2.3 DC/DC Converter Flexibility Enables Adding Noise Reduction Circuitry
Two simple noise reductions techniques that you can easily implement with a discrete DC/DC converter.
05:09
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3. Achieving low noise and high efficiency for noise-sensitive analog loads

Noise and EMI can be detrimental to sensitive analog signal chain circuitry. For this reason, many engineers automatically default to linear regulators. But, in doing so, they are essentially trading one problem (noise) for another (heat dissipation). In this section we will discuss what types of signal chain loads can be driven directly by a switching regulator to get low noise and EMI without sacrificing efficiency. We will also discuss when a linear regulator is absolutely needed to reach levels of noise not possible with a switcher.

Resources

Article: Designing a modern power supply for RF sampling converters

White paper: Low-EMI buck converter powers a multivariable sensor transmitter with BLE connectivity

TI Design: Less Than 1-W, Quad-Channel, Analog Output Module With Adaptive Power Management Reference Design

White paper: Power supply architecture comparison for a 12-bit analog to digital converter

Blog: Using a DC/DC converter to power an ADC

Blog: Low-noise charge pumps make it easy to create negative voltages

Blog: Powering up the performance of sensitive test and measurement systems

TI Design: Efficient, LDO-free Power Supply for a 12-bit 500-MSPS ADC Reference Design

TI Design: Efficient, LDO-Less, Power-Supply Network Reference Design for RF-Sampling ADC

TI Design: Low-Voltage, Low-Noise Power-Supply Reference Design for Ultrasound Front End

Training:

# Title Duration
3.1 Measuring Vout Ripple in DC/DC Converters
The video explains the measurement set-up for the output voltage ripple in DC/DC converters directly at the load with a high frequency bypass capacitor....
05:28
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4. Low EMI and low noise DC/DC conversion in Automotive applications

Because of the potential havoc that interference can wreak in radio and safety critical systems, automotive electronics are subject to the most stringent EMI standards- the most common being CISPR25 Class-5. The materials below provide a discussion around the sources of EMI in an automotive environment and a comprehensive blueprint to understanding how to minimize it's effects.

Resources

Blog: Build a sub-20W CISPR25 Class 5 power design for automotive infotainment processors

App Note: Designing High-Performance, Low-EMI Automotive Power Supplies

TI Design: Front End Power Supply Reference Design with Cold Crank Operation, Transient Protection, EMI Filter

TI Design: CISPR 25 Class 5 USB Type-C™ Port Reference Design with USB 3.0 Data Support

TI Design: CISPR 25 Class 5 Multi-Output Power Supply Reference Design for Rear Camera, Automotive ADAS Systems

Training:

# Title Duration
4.1 Optimizing Automotive DC/DC Converter Designs for EMI and Thermals
In this training we will talk about some of the most important features for automotive DCDC buck regulators and how they affect device performance. In...
45:16
4.2 Identifying the Key Features of an Automotive DC/DC Converter
What features to look for when you are selecting a DC/DC converter for automotive, including discussion of wide input voltage range, low quiescent current,...
24:13
4.3 Leveraging Spread Spectrum and Slew Rate Control in Automotive DC/DC Converter Designs
Learn how DC/DC converter features like spread spectrum and slew rate control can help you reduce EMI in your automotive power supply design.
09:57
4.4 How to Design Input EMI Filters for an Automotive DC/DC Converter
Learn how to design input EMI filters and how to debug an automotive DC/DC converter design to enhance EMI performance.
11:30
4.5 Eliminate High-Frequency Switch-Node Ringing and Pass CISPR 25 Class 5 without Metallic Shielding or a Common-Mode Choke
Get help passing CISPR 25 Class 5 with the EMI-optimized LMS3635-Q1 and LMS3655-Q1 automotive DC/DC buck converters
08:58
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