ISL6421
Single Output LNB Supply and Control Voltage Regulator with I²C Interface for Advanced Satellite Set-top Box Designs

Key Features

• Switch-Mode Power Converter for Lowest Dissipation
• Boost PWM with >92% Efficiency
• Selectable 13V or 18V Outputs
• Digital Cable Length Compensation (1V)
• External Pin to Select 13V/18V Options
• I²C Compatible Interface for Remote Device Control
• Registered Slave Address 0001 00XX
• Fully Functional 3.3V, 5V Operation up to 400kHz
• Built-In Tone Oscillator Factory Trimmed to 22kHz
• Facilitates DiSEqC (EUTELSAT) Encoding
• Internal Over-Temperature Protection and Diagnostics
• Internal Overload and Overtemp Flags (Visible on I²C)
• LNB Short-Circuit Protection and Diagnostics
• QFN Package
• Compliant to JEDEC PUB95 MO-220 QFN - Quad Flat No Leads - Product Outline
• Near Chip-Scale Package Footprint
• Pb-free available

Description

The ISL6421 is a highly integrated solution for supplying power and control signals from advanced satellite set-top box (STB) modules to the low noise block (LNB). This device is comprised of a current-mode boost PWM and a low-noise linear regulator, along with the circuitry required for I²C device interfacing and for providing DiSEqCTM standard control signals to the LNB.

A regulated output voltage is available at the output terminal (VOUT) to support the operation of the antenna port in advanced satellite STB applications. The regulated output may be set to either 13V or 18V by use of the voltage select command (VSEL) through the I²C bus. Additionally, to compensate for the voltage drop in the coaxial cable, the voltage may be increased by 1V with the line length compensation (LLC) feature. An enable command sent on the I²C bus provides standby mode control for the PWM and linear combination, disabling the output to conserve power.

A current-mode boost converter provides the linear regulator with an input voltage that is set to the required output voltage, plus 1.2V (typ.) to insure minimum power dissipation. This maintains a constant voltage drop across the linear pass element, while permitting an adequate voltage range for tone injection.

The device is capable of providing 450mA (typ.).

Applications

• LNB Power Supply and Control for Satellite Set-Top Box References