The ISL6423B 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 single antenna ports. The device consists of a current-mode boost PWM and a low-noise linear regulator along with the circuitry required for 22kHz tone generation, modulation, and I2C device interface. The device simplifies the total LNB supply design, making it simple, efficient, and compact with a low external component count. The current-mode boost converter provides the linear regulator with an input voltage that is set to the final output voltages, plus typically 0.8V to ensure minimum power dissipation across each linear regulator. This maintains a constant voltage drop across the linear pass element while permitting an adequate voltage range for tone injection. The final regulated output voltage is available at output terminals to support the operation of an antenna port for single tuners. The outputs for each PWM can be controlled in two ways, full control from I2C using the VTOP and VBOT bits, or set the I2C to the lower range i.e., 13V/14V, and switch to the higher range i.e., 18V/19V, with the SELVTOP pin. All the functions on this IC are controlled via the I2C bus by writing 8-bit words onto the System Registers (SR). The same register can be reused.
The ISL6423B is a highly integrated voltage regulator and I²C‑controlled interface IC designed to power and control low‑noise blocks (LNBs) in advanced satellite set‑top box modules. It combines a current‑mode boost PWM converter with a low‑noise linear regulator, providing selectable 13.3 V or 18.3 V outputs and a built‑in 22 kHz tone oscillator for DiSEqC encoding.
Key features include >92 % boost converter efficiency, 750 mA continuous output current, programmable over‑current limits, and full I²C register control for diagnostics, standby mode, and output selection. The device is offered in QFN and EPTSSOP packages and is RoHS‑compliant.
| Selectable Output Voltage | 13.3 V or 18.3 V |
|---|---|
| Continuous Output Current | 750 mA |
| Boost Converter Efficiency | >92 % |
| Temperature Range | -40 °C to +150 °C |
The device can deliver up to 750 mA of continuous output current.
All functions are controlled via the I²C bus by writing 8‑bit words to system registers, which can also be read back for diagnostics.
The regulator provides selectable output voltages of 13.3 V or 18.3 V.