FN9130 Rev 1.00

Page 1 of 11

Jul 2004

FN9130

Rev 1.00

Jul 2004

ISL6421

Single Output LNB Supply and Control Voltage Regulator with I2C Interface for

Advanced Satellite Set-top Box Designs

DATASHEET

The ISL6421 is a highly integrated solution for supplying

power and control signals from advanced satellite set-top

box (STB) modules to the low noise block (LNB). This device

is comprised of a current-mode boost PWM and a low-noise

linear regulator, along with the circuitry required for I2C

device interfacing and for providing DiSEqCTM standard

control signals to the LNB.

A regulated output voltage is available at the output terminal

(VOUT) to support the operation of the antenna port in

advanced satellite STB applications. The regulated output

may be set to either 13V or 18V by use of the voltage select

command (VSEL) through the I2C bus. Additionally, to

compensate for the voltage drop in the coaxial cable, the

voltage may be increased by 1V with the line length

compensation (LLC) feature. An enable command sent on

the I2C bus provides standby mode control for the PWM and

linear combination, disabling the output to conserve power.

A current-mode boost converter provides the linear regulator

with an input voltage that is set to the required output

voltage, plus 1.2V (typ.) to insure minimum power

dissipation. This maintains a constant voltage drop across

the linear pass element, while permitting an adequate

voltage range for tone injection.

The device is capable of providing 450mA (typ.).

Features

• Switch-Mode Power Converter for Lowest Dissipation

- Boost PWM with >92% Efficiency

- Selectable 13V or 18V Outputs

- Digital Cable Length Compensation (1V)

• External Pin to Select 13V/18V Options

•I2C Compatible Interface for Remote Device Control

- Registered Slave Address 0001 00XX

- Fully Functional 3.3V, 5V Operation up to 400kHz

• Built-In Tone Oscillator Factory Trimmed to 22kHz

- Facilitates DiSEqC (EUTELSAT) Encoding

• Internal Over-Temperature Protection and Diagnostics

• Internal Overload and Overtemp Flags (Visible on I2C)

• LNB Short-Circuit Protection and Diagnostics

• QFN Package

- Compliant to JEDEC PUB95 MO-220 QFN - Quad Flat

No Leads - Product Outline

- Near Chip-Scale Package Footprint

• Pb-free available

Applications

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

References

• Tech Brief 389 (TB389) - “PCB Land Pattern Design and

Surface Mount Guidelines for QFN Packages”; Available

on the Intersil website, www.intersil.com

Ordering Information

PART NUMBER

TEMP. RANGE

(oC)

PACKAGE

PKG.

DWG. #

ISL6421ER

-20 to 85

32 Ld 5x5 QFN L32.5x5

ISL6421ER-T

32 Ld 5x5 QFN Tape and Reel

L32.5x5

ISL6421ERZ

(See Note)

-20 to 85

32 Ld 5x5 QFN

(Pb-free)

L32.5x5

ISL6421ERZ-T

(See Note)

32 Ld 5x5 QFN Tape and Reel

(Pb-free)

L32.5x5

NOTE: Intersil Pb-free products employ special Pb-free material

sets; molding compounds/die attach materials and 100% matte tin

plate termination finish, which is compatible with both SnPb and

Pb-free soldering operations. Intersil Pb-free products are MSL

classified at Pb-free peak reflow temperatures that meet or exceed

the Pb-free requirements of IPC/JEDEC J Std-020B.