AN718

AN718 Vishay Siliconix AN718 Powering the Pentium™ VRE with the Si9145 Voltage Mode Controlled PWM Converter BENEFITS First and only Intel-approved switching converter solution to provide static and dynamic voltage regulation for the Pentium VRE microprocessor. Low cost Efficiency greater than 89% at 7 A Eliminates the need for heat sinks Supplies maximum currents required by P54C High operating frequency (recommended 375 kHz) allows use of the smallest possible inductors and capacitors, resulting in lowest voltage ripple and best transient response Easily adjustable output voltage to meet the different specs of P54C family. PCB layout available Available in SO-16 surface-mount package The Si9145BY consistently satisfies Pentium VRE voltage regulation limits within generous margins. Worst-case assumptions for voltage regulation, as provided by Intel, are displayed in Figure 2. REGULATION REQUIREMENTS FOR THE VRE PENTIUM CONVERTER The Pentium VRE microprocessor has been designed to operate faster and more efficiently than any of its predecessors. To save power, a CPU clock has been implemented with start/stop features, requiring an ultra-fast response from the power supply. To obtain higher clock speeds and to enhance manufacturing yields, the Pentium requires specific output voltage levels with tight voltage regulations (Figure 3). Within this stringent voltage regulation limit, no overshoot or undershoot are permitted to exceed the regulation limit, irres...