MAX8709B Datasheet, PDF (1/24 Pages) Maxim Integrated Products – High-Efficiency CCFL Backlight Controller with SMBus Interface

19-0768; Rev 0; 3/07
High-Efficiency CCFL Backlight
Controller with SMBus Interface
General Description
The MAX8709B integrated backlight controller is
optimized to drive cold-cathode fluorescent lamps
(CCFLs) using a resonant full-bridge inverter architecture.
The resonant operation maximizes striking capability and
provides near-sinusoidal waveforms over the entire input
range to improve CCFL lifetime. The controller operates
over a wide input voltage range of 4.6V to 28V with high
power-to-light efficiency. The device also includes safety
features that effectively protect against many single-point
fault conditions including lamp-out and short-circuit faults.
The MAX8709B achieves 10:1 dimming range by “chop-
ping” the lamp current on and off using a digital pulse-
width-modulation (DPWM) method. The minimum DPWM
duty cycle of the MAX8709B is 12.5%. The brightness is
controlled with a 2-wire SMBus™-compatible interface.
The device directly drives the four external N-channel
power MOSFETs of the full-bridge inverter. An internal
5.3V linear regulator powers the MOSFET drivers, the
DPWM oscillator, and most of the internal circuitry. The
MAX8709B is available in a space-saving 28-pin
thin QFN package and operates over a -40°C to +85°C
temperature range.
Applications
Notebook Computer Displays LCD TVs
LCD Monitors
Automotive Displays
SMBus is a trademark of Intel Corp.
VIN
BATT
VCC
GND
VDD
BST2
LOT
BST1
REF
GH1
MAX8709B
LX1
ILIM
LX2
GL1
CCV
PGND
CCI
GL2
GH2
SUS
VFB
SDA
ISEC
SCL
IFB
Features
♦ Synchronized to Resonant Frequency
Longer Lamp Life
Guaranteed Striking Capability
High Power-to-Light Efficiency
♦ Wide Input Voltage Range (4.6V to 28V)
♦ Feed Forward for Excellent Line Rejection
♦ SMBus Dimming Control Interface
♦ 10:1 Dimming Range
♦ Guaranteed 200Hz to 220Hz DPWM Frequency
♦ Secondary Voltage Limit Reduces Transformer
Stress
♦ Adjustable Lamp-Out Protection with 1s Timer
♦ Secondary Current Limit Protects Against High-
Voltage Short Circuits to Ground
♦ Small, 5mm x 5mm, Thin QFN Package
PART
MAX8709BETI
Ordering Information
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 28 Thin QFN 5mm x 5mm
Pin Configuration appears at end of data sheet.
Minimal Operating Circuit
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.