ISL6405 Dual Output LNB Supply and Control Voltage Regulator with I

The ISL6405 is a highly integrated voltage regulator and interface integrated circuit (IC) designed to supply power and control signals from advanced satellite set-top box (STB) modules to the low noise blocks (LNBs) of two antenna ports. This device features two independent current-mode boost pulse width modulators (PWMs) and two low-noise linear regulators, along with the necessary circuitry for 22kHz tone generation, modulation, and I2C device interface. The ISL6405 simplifies the overall LNB supply design, making it efficient and compact with a low external component count. The two independent current-mode boost converters provide the linear regulators with input voltages set to the final output voltages, typically plus 1.2V, ensuring minimal power dissipation across each linear regulator. This design maintains constant voltage drops across each linear pass element while allowing for an adequate voltage range for tone injection. The final regulated output voltages are available at two output terminals to support the simultaneous operation of two antenna ports for dual tuners. The output voltages for each PWM can be set to 13V or 18V through independent voltage select commands (VSEL1, VSEL2) via the I2C bus. Additionally, to account for voltage drop in the coaxial cable, the selected voltage may be increased by 1V using the line length compensation (LLC) feature. All functions of this IC are controlled via the I2C bus, which allows for writing 8 bits to the System Register (SR, 8 bits). This register can also be read back, with two bits reporting the diagnostic status. Separate enable commands on the I2C bus provide independent standby mode control for each PWM and linear combination, allowing for output shutdown. Each output channel can deliver a continuous current of 750mA, with the overcurrent limit being digitally programmable. The SEL18V pin in the QFN package facilitates the transition from 13V to 18V through an external pin, overriding the I2C input.

The ISL6405 IC operates by integrating multiple functionalities into a single package, which enhances the efficiency of satellite communication systems. The dual boost converters are essential for generating the required high output voltages necessary for powering LNBs, which are critical in receiving satellite signals. The ability to select between 13V and 18V output allows for flexibility in system design, accommodating various LNB specifications.

The incorporation of I2C communication facilitates easy interfacing with microcontrollers or other digital systems, enabling precise control over the voltage outputs and monitoring of system status. The line length compensation feature is particularly significant in practical applications, as it mitigates the effects of voltage drop due to long cable runs, ensuring consistent performance of the LNBs.

Furthermore, the current capacity of 750mA per channel is substantial for most satellite applications, while the programmable overcurrent limit provides an added layer of protection against potential faults. The independent enable commands for each channel enhance system reliability, allowing for selective power management and reducing overall power consumption when certain channels are not in use.

Overall, the ISL6405 presents a robust solution for modern satellite set-top box applications, combining multiple power management functions into a compact and efficient design, thereby streamlining the development of satellite communication systems.The ISL6405 is a highly integrated voltage regulator and interface IC, specifically designed for supplying power and control signals from advanced satellite set-top box (STB) modules to the low noise blocks (LNBs) of two antenna ports. The device is comprised of two independent currentmode boost PWMs and two low-noise linear regulators along with

the circuitry required for 22kHz tone generation, modulation and I2C device interface. The device makes the total LNB supply design simple, efficient and compact with low external component count. Two independent current-mode boost converters provide the linear regulators with input voltages that are set to the final output voltages, plus typically 1.

2V to insure minimum power dissipation across each linear regulator. This maintains constant voltage drops across each linear pass element while permitting adequate voltage range for tone injection. The final regulated output voltages are available at two output terminals to support simultaneous operation of two antenna ports for dual tuners.

The outputs for each PWM are set to 13V or 18V by independent voltage select commands (VSEL1, VSEL2) through the I2C bus. Additionally, to compensate for the voltage drop in the coaxial cable, the selected voltage may be increased by 1V with the line length compensation (LLC) feature.

All the functions on this IC are controlled via the I2C bus by writing 8 bits on System Register (SR, 8 bits). The same register can be read back, and two bits will report the diagnostic status. Separate enable commands sent on the I2C bus provide independent standby mode control for each PWM and linear combination, disabling the output into shutdown mode.

Each output channel is capable of providing 750mA of continuous current. The overcurrent limit can be digitally programmed. The SEL18V pin with QFN package allows the 13V to 18V transition with an external pin, over-riding the I2C input. 🔗 External reference