1
®
FN9167.3
ISL6421A
Single Output LNB Supply and Control
Voltage Regulator with I
2
C Interface for
Advanced Satellite Set-top Box Designs
The ISL6421A is a highly integrated solution for providing
power and control signals from advanced satellite set-top
box (STB) modules to the low noise block (LNB). The
internal architecture of this device contains a current-mode
boost PWM and a low-noise linear regulator, along with the
circuitry required for I
2
C device interfacing and for providing
DiSEqC™ 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 bit (VSEL) through the I
2
C bus. Additionally, to
compensate for the voltage drop in the coaxial cable, the
voltage may be increased by 1V with the line length
compensation bit (LLC) feature. The device can be put into a
standby mode by means of the enable bit (EN), this disables
the PWM and Linear regulator combination and helps
conserve power.
The input to the linear regulator is derived from the current
mode boost converter, such that the required voltage is the
sum of the output voltage and the linear regulator drop (1.0V
typical). This ensures that the power dissipation is minimized
and 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 (typical). The
overcurrent limit is either digitally or resistor programmable.
Pinout
ISL6421A (QFN) TOP VIEW
Features
• Switch-Mode Power Converter for Lowest Dissipation
- Boost PWM with >92% Efficiency
- Selectable 13V or 18V Outputs
- Digital Cable Length Compensation (1V)
- Vsw tracks Vout ensures low dissipation
•I
2
C 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
- External Modulation input DSQIN
• Internal Over Temperature Protection and Diagnostics
• Internal Overload and Over Temperature Flags
(Visible on I
2
C)
• Output Back-Bias Protection to 24V
• 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
• External Pins to Select 13V/18V Options
• Pb-Free Available (RoHS Compliant)
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
PGND
NC
SGND
SEL18V
NC
BYPASS
PGND
CS
FB
COMP
VSW
NC
ADDR
SDA
GATE
CPSWOUT
NC
NC
NC
AGND
VOUT
DSQIN
TCAP
SCL CPSWIN
CPVOUT
VCC
NC
NC
NC
NC
NC
1
2
3
4
5
6
7
8
24
23
22
21
20
19
18
17
32 31 30 29 28 27 26 25
9 10111213141516
Ordering Information
PART
NUMBER*
PART
MARKING
TEMP.
RANGE
(°C) PACKAGE
PKG.
DWG. #
ISL6421AER ISL6421AER -20 to 85 32 Ld 5x5 QFN L32.5x5
ISL6421AERZ
(Note)
ISL6421AERZ -20 to 85 32 Ld 5x5 QFN
(Pb-free)
L32.5x5
*Add -T for tape and reel package.
NOTE: Intersil Pb-free products employ special Pb-free material sets;
molding compounds/die attach materials and 100% matte tin plate
termination finish, which are RoHS compliant and 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-020.
Data Sheet
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 registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2004-2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
March 9, 2006
