ISL6405 Dual Output LNB Supply and Control Voltage Regulator with I

Posted on Feb 5, 2014

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

ISL6405 Dual Output LNB Supply and Control Voltage Regulator with I
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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...

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