Analog Circuit Design Volume Three

Chapter 27

Switching regulator generates both positive and negative supply with a single inductor

Brian Huffman

Abstract

The use of a switching regulator to generate both positive and negative supply with a single inductor is described.

Keywords

Switching regulator

LT1172

Many systems require ±12V from a 5V input. Analog or RS232 driver power supplies are obvious candidates. This requirement is usually solved by using a switcher with a multiple-secondary transformer or multiple switchers. These solutions can be complicated, requiring either transformer design or two inductors. An alternative approach, shown in Figure 27.1, uses a single inductor and charge pump to obtain the dual outputs. This solution is particularly noteworthy because ...