New-Tech Europe | December 2016 | Didital Edition

voltage and switching frequency, and provide protection against over current and over voltage conditions. 5. Ideally require no external compensation - this can otherwise be a time consuming task to ensure design stability over worst-case conditions of input/output voltages and load currents. 6. Provide a solution that can fit in tight spaces without compromise. 7. Achieve “plug-and-play” simplicity, requiring no system troubleshooting once the PCB is properly designed. 8. Achieve all of the above objectives at a low cost in medium to large volumes. The significance of these points can be appreciated by considering a modest subsystem that needs to provide five rails with output voltages ranging from 0.6V to 3.3V and operate from an input voltage of 5V 20V. A buck (step-down) DC-DC converter might typically be used to generate each of these rails, as illustrated by the simplified functional schematic in figure 1. But, implemented as a discrete solution, such a design can easily take from two to four months, with a good part of the time spent ensuring that the stability of the control loops and the resulting transient response of the outputs can be unconditionally guaranteed over worst case temperature conditions and across the 6 sigma distribution of discrete component parameter values. This length of time, in some cases, can make or break the chance of a new product making it to market ahead of the competition. Greater integration helps

Figure 1: Simplified functional circuit schematic of a COT buck (step-down) switching regulator

Figure 2. The QFN package used for Exar’s XR79106 power module provides pads that ensure excellent thermal conductivity

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