1.8 Power management  (Page 4/7)

You should know several other critical terms/definitions, including dropout , PSRR , and quiescent current . Reference 1 provides a complete explanation of these and other important specifications/parameters associated with power supply circuits. Reference 2 and Reference 3 are comprehensive textbooks that cover most aspects of power-converter design. Some power-converter circuits have multiple modes of operation to maximize efficiency over a wide load range. The concepts of fixed- and variable-frequency operation, including pulse-width modulation (PWM) and pulse-frequency modulation (PFM), are discussed in Reference 10.

Understanding the data sheet: voltage regulator component selection

For these examples, please refer to the TPS54140A and TPS62160 data sheets, along with the text below.

Just like an op amp data sheet, a voltage regulator data sheet can also be somewhat overwhelming. Numerous parameters are listed for a device with (relatively) few pins. But as noted in the chapter on op amps, the front page will generally provide a quick summary of features and suggested applications that will indicate the typical intended uses of the device. As with other analog IC devices (like the op amp), some specific parameters may be more important than others for a given application. The typical performance graphs can also give some fundamental information about how the device will perform under different operating conditions – this information may not be guaranteed for all conditions, but it can tell you much about the basic characteristics of the part. The electrical specifications tables will provide guaranteed maximum and minimum values of certain critical parameters, subject to the test conditions defined at the top of each table.

The applications section will offer some discussion about how to use the device, and calculation procedures for selecting external components such as inductors and capacitors. It provides tips, warnings and advice on how to best use the device. Finally, most devices will also have an evaluation module (EVM) available. Even if you do not use the EVM, you can download the EVM user guide and schematic from the product data folder at www.ti.com and get a detailed schematic, recommended external components, test procedures and PCB layout for each device.

The Web-based selection tools and component landing pages on the TI website will typically provide basic information about whether a component can be used for a particular requirement. However, in many cases, there may be multiple devices that appear to satisfy the same requirement – to understand which of these devices is the best fit requires a slightly deeper understanding of the application requirements and a more complete review of the critical parameters of a device based on the component data sheet.

As an example, consider a system design requirement to generate a precisely regulated 3.3-V output from a poorly regulated 12-V input, delivering up to 1 A of output current to the load. There are many ways to solve this problem. The best way depends on the additional requirements of the application, and understanding which of the key performance parameters are most important. For example, the most efficient solution may not be the lowest cost. Or perhaps efficiency is nice to have but not as important as rugged, robust design and tolerance to high-voltage transients in a noisy environment. Or it may be necessary to find a physically very small solution to fit in a tightly constrained space for a portable product.