8284

8284 ADVANCE INFORMATION (Subject to change without notice) December 22, 2000 TWO-OUTPUT LNB SUPPLY AND CONTROL-VOLTAGE REGULATOR Intended for analog and digital satellite receivers, the low noise block converter regulator (LNBR) is a monolithic linear and switching voltage regulator designed to provide power and interface signals to the LNB downconverter via the coaxial cable. Because most satellite receivers have two antenna ports, the output voltage of the regulator is available at one of two logic-selectable output terminals (LNBA, LNBB). If the device is in stand-by mode (EN terminal LOW), both regulator outputs are disabled, allowing the antenna downconverters to be supplied and controlled by other satellite receivers sharing the same coaxial cable. Similar single-output devices, with a bypass function for slave operation in single-dish dual-receiver systems, are the A8283SB/SLB. The regulator outputs are set to 12, 13, 18, or 20 V by the VSEL terminals. Additionally, it is possible to increase the selected voltage by 1 V to compensate for the voltage drop in the coaxial cable (LLC terminal HIGH). The LNBR combines a tracking switching regulator and low-noise linear regulators. Logic inputs (VSEL0, VSEL1, and LLC) select the desired output voltage. A tracking current-mode buck converter provides the linear regulator input voltage that is set to the output voltage plus typically 0.8 V. This maintains constant voltage drop across the linear regulators while permitting ad...