U-100A UC3842/3/4/5 Provides Low-Cost Current-Mode Control

The fundamental challenge of power supply design is to realize simultaneously two conflicting objectives: good electrical performance and low cost. The UC3842/3/4/5 control ICs are integrated pulse-width modulators (PWMs). These inexpensive IC controllers provide all the performance advantages of current-mode operation. In addition, the UC3842 series is optimized for efficient power-sequencing of off-line converters, for DC-to-DC regulators, and for driving power MOSFETs or transistors. This application note provides a functional description of the UC3842 family and highlights the features of each individual member: the UC3842, UC3843, UC3844 and UC3845. A review of current-mode control and its benefits is included, and methods of avoiding common pitfalls are mentioned. The final section presents designs of power supplies that use UC3842 control.