1

Single Output LNB Supply and Control Voltage Regulator

ISL9492

The ISL9492 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 (LNB) of a single antenna port. It also supports

DiSEqC tone generation and modulation with diagnostic status

writing 8 bit words onto the System Registers (SR).

The device design makes the total LNB supply design simple,

efficient and compact with low external component count by

integrating Boost power MOSFET, current-mode boost PWM and

a low-noise linear regulator. The current-mode boost converters

provide the linear regulator with input voltage that is set to the

final output voltages, plus typically 0.9V to insure minimum

power dissipation across each linear regulator.

The LNB output voltage can be controlled in two ways; by full control

lower range and switching to higher range with the select VTOP pin.

The External modulation input EXTM accepts a modulated DISEqC

command and transfers it symmetrically to the output. The EXTM

pin can be used to modulate the continuous internal tone. The fault

signal serves as an interrupt for the processor when any condition

turns OFF the LNB controller (over-temperature, overcurrent,

disable). The states of these flags to the faults can be thoroughly

Features

• Single-Chip Power Solution

- Operation for 1-Tuner/1-Dish Applications

• Integrated Boost MOSFET

• Switch-Mode Power Converter for Lowest Dissipation

- 490kHz Boost Switching Frequency

- Boost PWMs with > 92% Efficiency

- Selectable 13.5V or 18.5V Outputs

• 31V Output Back-Bias Capability

• Built-in Tone Oscillator Factory

- Facilitates DiSEqC (EUTELSAT) Encoding

-Trimmed to 22kHz

- External Modulation Input

• DiSEqC 2.0 Support and Diagnostics

• Internal Overvoltage, Undervoltage, Overcurrent Protection,

and Fault Signal Status Pin

• Short-Circuit Protection

Applications

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

FIGURE 1. TYPICAL APPLICATION

R1

100k

C4

1µF

C8

0.22µF

C9

0.22µF

C6

0.1µF

C10

100µF

C11

10µF

NDS356AP

L1

10µH

L3

220µH

R2

15

FLT#

SCL

SDA

CPVOUT

27

CPSWOUT

28

CPSWIN

1

VCC

6

LDO_SGND

20

LDO_SGND

25

ABYP

5

PGND

9

DGATE 23

NC 4

TCAP 22

DBYP 10

SDA 16

SCL 17

FLT# 21

ISL9492

D1

CMS06

L2

1µH

C7

100µF

C5

2.2nF

C1

0.047µF

C2

1µF

C3

1µF

EXTM

TDOUT

TXT

LNB

POWER

VIN

C10

0.1µF

3.3V

Q1

D4

CMS06

Rp

100

FERRITE

BEAD

100

RL

Cp

See pg 14

March 17, 2011

FN6547.1

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

1-888-INTERSIL or 1-888-468-3774

Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.

All other trademarks mentioned are the property of their respective owners.