MAX8722C Datasheet, PDF (1/21 Pages) Maxim Integrated Products – Low-Cost CCFL Backlight Controller

19-3321; Rev 3; 2/09
EVAALVUAAILTAIOBNLEKIT
Low-Cost CCFL Backlight Controller
General Description
The MAX8722C 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 MAX8722C 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 5.4V linear regulator
powers the MOSFET drivers, the DPWM oscillator, and
most of the internal circuitry. The MAX8722C 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
Pin Configuration
Features
o Synchronized to Resonant Frequency
Longer Lamp Life
Guaranteed Striking Capability
High Power to Light Efficiency
o Wide Input Voltage Range (4.6V to 28V)
o Input-Voltage Feed-Forward for Excellent Line
Rejection
o Accurate Dimming Control with Analog Interface
o 10:1 Dimming Range
o Adjustable Accurate DPWM Frequency with Sync
Function
o Adjustable Lamp Current Rise and Fall Time
o Secondary Voltage Limit Reduces Transformer
Stress
o Lamp-Out Protection with Adjustable Timeout
o Secondary Overcurrent Protection with
Adjustable Timeout
o Low-Cost, 24-Pin QSOP Package
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX8722CEEG -40°C to +85°C 24 QSOP
PKG
CODE
E24-1
Minimal Operating Circuit
TOP VIEW
BATT 1
SHDN 2
ILIM 3
TFLT 4
CNTL 5
DPWM 6
SYNC 7
FREQ 8
COMP 9
IFB 10
VFB 11
ISEC 12
MAX8722C
24 GND
23 V_CC
22 V_DD
21 PGND
20 GL2
19 GL1
18 GH1
17 LX1
16 BST1
15 BST2
14 LX2
13 GH2
QSOP
VIN
VCC
BATT
VDD
GND
VCC
VCC
BST2
BST1
GH1
ILIM
MAX8722C _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 Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.