It doesn’t seem difficult to build a basic step-down (buck) DC/ DC regulator for low voltages of 10 volts (typical) or less and modest current levels of about 2 to 15 amperes (A). The designer just needs to select a suitable switching regulator IC and add a few passive components using the example circuit on the datasheet or application note. But is the design really done and ready to release to pilot run, or even to production? Probably not. While the regulator provides the desired DC rail, it still has several potential problems and issues. First, the efficiency may not meet project objectives or regulatory requirements, thereby adding to thermal impact, as well as shorter battery life. Second, additional components may be needed to ensure proper start-up, transient
performance, and low ripple, which in turn affects size, time to market, and the overall bill of material (BOM). Finally, and perhaps most challenging, the design may not meet the increasingly stringent limitations on electromagnetic interference (EMI) or radio frequency interference (RFI) as defined by the various regulatory mandates, thus requiring a redesign or further additional components and testing. This article describes the gap between expectations and performance between a basic DC/DC regulator design and a superior one that meets or exceeds requirements for efficiency, low radiated and ripple noise, and overall integration. The article then introduces Analog Devices’ Silent Switcher µModules and shows how to use them to solve multiple DC/ DC buck regulator problems.
ICs make it look easy, at first
Step-down DC/DC (buck) regulators are widely used to provide DC rails. A typical system may have tens of these providing different rail voltages or physically separated rails at the same voltage. These buck regulators commonly take a higher voltage, typically between 5 and 36 volts DC, and regulate it down to a single-volt value at a few or low double-digit amperes ( Figure 1 ).
There’s good news and bad news when constructing a
basic buck regulator. The good news is that building one that provides nominally “good- enough” performance is generally not difficult. There are many switching ICs available to do the bulk of the task that need only a single field effect transistor (FET) (or none at all) and a few
How to address DC/ DC noise, efficiency, and layout issues using integrated power modules By Bill Schweber
Contributed By DigiKey's North American Editors
Figure 1: The role of the DC/DC regulator (converter) is straightforward: Take an unregulated DC source which may be from a battery or a rectified and filtered AC line, and provide a tightly regulated DC rail as the output. (Image source: Electronic Clinic)
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