MAX8722 Datasheet, PDF (1/20 Pages) Maxim Integrated Products – Low-Cost CCFL Backlight Controller

19-3321; Rev 0; 6/04
EVAALVUAAILTAIOBNLEKIT
Low-Cost CCFL Backlight Controller
General Description
The MAX8722 integrated backlight controller is opti-
mized to drive cold-cathode fluorescent lamps (CCFLs)
using a full-bridge resonant inverter architecture.
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 (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 MAX8722 achieves 10:1 dimming range by “chop-
ping” the lamp current on and off using a digital pulse-
width modulation (DPWM) method. The DPWM frequency
can be accurately adjusted with a resistor or synchro-
nized to an external signal. The brightness is controlled
by an analog voltage on the CNTL pin. The device direct-
ly 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 MAX8722 is available in
a low-cost, 24-pin QSOP package and operates over a
-40°C to +85°C temperature range.
Applications
Notebook Computer Displays
LCD Monitors
LCD TVs
Features
♦ Synchronized to Resonant Frequency
Longer Lamp Life
Guaranteed Striking Capability
High Power to Light Efficiency
♦ Wide Input Voltage Range (4.6V to 28V)
♦ Input-Voltage Feed-Forward for Excellent Line
Rejection
♦ Accurate Dimming Control with Analog Interface
♦ 10:1 Dimming Range
♦ Adjustable Accurate DPWM Frequency with Sync
Function
♦ Adjustable Lamp Current Rise and Fall Time
♦ Secondary Voltage Limit Reduces Transformer
Stress
♦ Lamp-Out Protection with Adjustable Timeout
♦ Secondary Overcurrent Protection with
Adjustable Timeout
♦ Low-Cost 24-Pin QSOP Package
PART
MAX8722EEG
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
24 QSOP
Minimal Operating Circuit
Pin Configuration
VIN
TOP VIEW
BATT 1
24 GND
VCC
SHDN 2
ILIM 3
TFLT 4
CNTL 5
MAX8722
23 V_CC
22 V_DD
21 PGND
20 GL2
DPWM 6
19 GL1
SYNC 7
18 GH1
FREQ 8
17 LX1
COMP 9
16 BST1
IFB 10
15 BST2
VFB 11
14 LX2
ISEC 12
13 GH2
QSOP
VCC
BATT
VDD
GND
VCC
BST2
BST1
GH1
ILIM
MAX8722 _LX1
LX2
FREQ
GL1
SHDN
CNTL
SYNC
DPWM
COMP
TFLT
PGND
GL2
GH2
VFB
ISEC
IFB
________________________________________________________________ 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.