Switching Buck Controller Powers Pentium III Motherboards

Unlike earlier Intel Pentium processors, the Pentium III CPU requires five different voltages, which can mean bulky, expensive motherboard power supplies. The CS51313 switching buck controller is said to make it easy to power Pentium III boards. The solution involves the controller’s V_REF pin and a small external quad op amp. The controller powers V_CORE at 2V, and the V_REF quad op amp implements four linear regulators at 1.5V, 2.5V, 1.8V and 1.5V/3.3V selectable for V_DDQ. On-chip control and protection features simplify design and the use of multi-function pins minimizes size.One advantage is that the external op amp may be placed anywhere on the board, allowing layout flexibility. The external reference makes it easy to implement additional linear regulators. The CS51313 also uses the firm’s V² control architecture, which provides simple loop compensation to eliminate guesswork.