8283

Short-Circuit Protected Bypass Function for Slave Operation
LNB Selection and Stand-By Function
Built-In Tone Oscillator Factory Trimmed to 22 kHz, Facilitates
DiSEqC^(TM) (a trademark of EUTELSAT) Encoding
Full Modulation With No Load
Tracking Switch-Mode Power Converter for Lowest Dissipation
Externally Adjustable Short-Circuit Protection
LNB Short-Circuit Protection and Diagnostics
Auxiliary Modulation Input
Cable Length Compensation
Internal Over-Temperature Protection

A8283SB is intended for analog and digital satellite receivers, the low-noise blockconverter regulator (LNBR) is a monolithic linear and switching voltage regulator designed to provide power and interface signals to the LNB down converter via the coaxial cable.  If A8283SB is in stand-by mode (EN terminalLOW), the regulator output is disabled, allowing the antenna downconverters to be supplied or controlled by other satellite receivers sharing the same coaxial cable.  Similar two-output LNB supply and control voltage regulators are the A8284SB/SLB.

For slave operation in single-dish dual-receiver systems, the bypass function is implemented by an electronic switch between the master input terminal ^(MI) and the LNB terminal, leaving all LNB power and control functions to the master receiver.  This electronic switch is closed if the device is powered, EN is HIGH, and OSEL is LOW.

The regulator outputs are set to 12, 13, 18, or 20 V by the VSEL terminals.Additionally, A8283SB is possible to increase the selected voltage by 1 V to compen-sate for the voltage drop in the coaxial cable (LLC terminal HIGH).  The LNBR combines a tracking switching regulator and low-noise linear regulator.Logic inputs (VSEL₀, VSEL₁, and LLC) select the desired output voltage.  A tracking current-mode buck converter provides the linear regulator with an input voltage that is set to the output voltage plus typically 0.8 V. This main-tains constant voltage drop across the linear regulator while permitting ad-equate voltage range for tone injection.

The device is supplied in a 24-pin plastic DIP with batwing tabs (A8283SB), or a 24-lead SOIC power-tab package (A8283SLB).  In both cases,the power tab is at ground potential and needs no electrical isolation.