SI9117

Si9117 Vishay Siliconix High-Frequency Converter for Telecom Applications FEATURES D D D D On-board high-voltage, 1-W Switching FET Switching Frequencies of Up to 1 MHz Synchronization Capability Easily Compensated Current-Mode Operation D D D D Operates with Input Voltages Up to 200 V 1.8-MHz Error Amplifier Soft-Start Latched SHUTDOWN DESCRIPTION The Si9117 high-efficiency converter for telecom systems running off 48 V is ideal for emerging applications such as interactive video (IV) set-top boxes and microcell base stations, such as those used for Personal Communications Systems (PCS). IV set-top boxes and microcell base stations typically require less than 15 W of power and have access to the analog telephone line power. Both IV set-top boxes and microcell base stations process extremely low-level, modulated analog signals (on the order of mVs), making the frequency and energy content of radiated and conducted noise a major issue. These application circuits are also constrained in terms of available board space and place a premium on minimal footprint. Processing high-frequency, modulated analog signals for video or RF requires receivers with sensitivities in the range of 0.5 to 25 mV. At these levels, noise generated by switchmode power conversion can impair the signal recovery process. Controlling radiated noise is a matter of proper layout and shielding. Controlling conducted noise is a matter of limiting its energy and isolating the conducted energy’s fundamental an...