LM78S40 pdf datasheet

In modern electronic systems, voltage regulation is a basic
function required by the system for optimal performance.
The regulator provides a constant output voltage irrespective
of changes in line voltage, load requirements, or ambient
temperature.
For years, monolithic regulators have simplified
power-supply design by reducing design complexity, improving
reliability, and increasing the ease of maintenance. In the
past, monolithic regulator systems have been dominated by
linear regulators because of relatively low cost, low external
component count, excellent performance, and high reliability.
However, limitations to applicability and performance of linear
regulators can force the user to other more complex
regulator systems, such as the switching regulator.
Because of improvements in components made especially
for them, switching-regulated power supplies have proliferated
during the past few years. The emergence of inexpensive,
high-speed switching power transistors, low-loss ferrites
for inductor cores, and low-cost LSI circuits containing
all necessary control circuitry has significantly expanded the
range of switching regulator application.
This application note describes a new integrated subsystem
that contains the control circuitry, as well as the switching
elements, required for constructing switching regulator systems
(Figure 1). The principle of operation is discussed, a
complete system description provided, and the analysis and
design of the basic configurations developed. Additional information
concerning selection of external switching elements
and design of the inductor is provided.