ISL9491集成電路（IC）的特殊用途穩(wěn)壓器規(guī)格書(shū)PDF中文資料

These devices are 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. Each device consists of a current-mode boost

converter and a low-noise linear regulator along with the

circuitry required for tone injection and pin controllable

interface. The device makes the total LNB supply design

simple, efficient and compact with low external

component count.

The current-mode boost converters provide the linear

regulator with input voltage that is set to the voltage at

the VOUT pin plus a minimal drop to insure minimum

power dissipation across the internal LDO. This maintains

constant voltage drop across the linear pass element

while permitting adequate voltage range for tone

injection.

The final regulated output voltage is available at the

cathode of the back diode to support the operation of an

antenna port for a single tuner. The outputs can be set to

various voltage level for the desired polarization

reception by means of the logic presented to the VSET0

and VSET1 pins. An EN pin is to be driven high to enable

the outputs for the PWM and linear combination; setting

EN low disables the output, forcing a shutdown mode.

The external modulation input (EXTM) can accept a tone

modulated DiSEqC command and transfer it

symmetrically to the output to meet DiSEqC 1.x protocol.

An external DiSEqC tank circuit can also be implemented

to support DiSEqC 2.x.

Features

? Single Chip Power Solution

- Operation for 1-Tuner/1-Dish Applications

? Switch-Mode Power Converter for Lowest Dissipation

- Boost PWMs with >92 Efficiency

- Pin Controllable Enable and Output

? 2.5V/3.3V/5V Logic Compatible

? FAULT Signal

? DIRECTV SWM Compliant

? VSET Pin to Toggle between Vertical and Horizontal

Polarizations

? External Tone Input

? Internal Overcurrent and Over-Temperature

Protection

? Pb-Free (ROHs Compliant)

Applications

? LNB Power Supply and Control for Satellite Set-Top

Box