EMI characteristics——This application note describes electromagnetic interference (EMI) for different standards and regulations; how these standards and rules relate to DC/DC power modules, recommendations for external filtering solutions, recommended PCB design and grounding design. Input system instability——This application note details the conditions under which the input system is unstable because the DC/DC converter appears as a negative resistance load. This note describes the cause of this instability and shows a preferred solution to correct it. Output load current calculation——This application note provides an easy way to calculate the output load current by using a current-sampling resistor on an open-frame DC/DC converter. All equations, conversion rates and sampling resistor values are included. Output voltage ripple measurement——This application note explains the occasional high frequency noise spurs when measuring output voltage ripple on the converter and how these burrs were manually introduced during measurement. This paper details how to eliminate this measurement error with appropriate test equipment and terminal processing methods. Pad venting hole study——This application note has been published on the issue of high current (greater than 60A) through the gold-plated pad vias when the pin and PCB board heat increases. A detailed thermal analysis will show that when a single heat sink hole is used, the internal heat generation and the temperature rise of the power converter and load board are small. Current sharing of all featured modules——This application note details the additional features available in the full featured module. This feature provides an easier way to use active current sharing features for N+1 and parallel applications. Interpretation of 100V input transient protection——This application note is an overview of the input transient protection features and explains the differences in the protection levels of our DC/DC converter product lines. It also answers some questions about these features that are often mentioned. Define an intelligent pinout for high current DC/DC converters——Output pin design for high current converters (greater than 60A) for two sets of output pins. This design refines voltage drop and power consumption, creating a priority solution for customers.
What is the best strategy to minimize EMI?
There is no perfect EMI strategy in any application, but some basic ideas can make this task a lot easier. The first step is to ensure that the positional layout of the components minimizes noise. For example, the decoupling capacitor should be located as close as possible to the converter, especially the X and Y capacitors. Ground planes are used to minimize radiative coupling, minimizing cross-combination of sensitive nodes, and minimizing cross-combination of large current nodes that radiate these noises from common mode capacitors. The position of the EMI component is critical to avoid placing the converter too close to your filter to avoid noise coupling back into the filter. Remember: you are filtering not just the power supply, but all the circuits that the converter is supplying. Most communications cabinets today use as much local filtering as possible on the board level, followed by another filter in the power input module, from which power inflows will enter your cabinet.
What type of conduction input filter should I use?
A pre-designed EMI filter may be sufficient for a particular converter, but there is no guarantee that it will suppress EMI conducted by other sources on the board, such as noise from high-speed processors and other digital logic devices. . Better values and performance will be obtained through a discrete filtering design. The key to a smooth EMI compliance process is to design as many filters as possible into your circuit pack. This will allow for flexibility in fine-tuning and modifying components as the initial test proceeds. The best way is to pre-multiple designs rather than unconsciously being discovered. Once the initial test is complete, the components are easy to remove. In contrast, adding components to an existing PCB design is much more difficult and produces unpredictable results. Typically, most modern communication devices use a local EMI filter and a final shielding filter placed at or near the power input module on each board card.
What if there is no casing?
Although it is preferable to use it organically, it is not mandatory. In some environments, the chassis of the input conductive EMI filter is not available. If this is the case, you will want to use a different filter topology.