INTRODUCTION

　　The use of switching regulators increased dramatically in the 1980’s and this trend remains strong going into the 90s. The reasons for this are simple; heat and efficiency. Today’s systems are shrinking continuously， while simultaneously offering greater electronic “horsepower.” This combination would result in unacceptably high internal temperatures if low efficiency linear supplies were used. Heat sinks do not solve the problem in general because most systems are closed， with low thermal transfer from “inside” to “outside.”

　　Battery-powered systems need high efficiency supplies for long battery life. Topological considerations also require switching technology. For instance， a battery cannot generate an output higher than itself with linear supplies. The availability of low cost rechargeable batteries has created a spectacular rise in the number of battery-powered systems， and consequently a matching rise in the use of switching regulators.

　　The LT?1074 and LT1076 switching regulators are designed specifically for ease of use. They are close to the ultimate “three terminal box” concept which simply requires an input， output and ground connection to deliver power to the load. Unfortunately， switching regulators are not horseshoes， and “close” still leaves room for egregious errors in the final execution. This application note is intended to eliminate the most common errors that customers make with switching regulators as well as offering some insight into the inner workings of switching designs. There is also an entirely new treatment of inductor design based on the mathematical models of core loss and peak current. This allows the customer to quickly see the allowable limits for inductor value and make an intelligent decision based on the need for cost， size， etc. The procedure differs greatly from previous design techniques and many experienced designers at first think it can’t work. They quickly become silent after standard laborious trial-and-error techniques yield identical results.