Document
19-3321; Rev 3; 2/09
KIT ATION EVALU E L B AVAILA
Low-Cost CCFL Backlight Controller
General Description 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
MAX8722C
The MAX8722C integrated backlight controller is optimized 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 “chopping” the lamp current on and off using a digital pulsewidth modulation (DPWM) method. The DPWM frequency can be accurately adjusted with a resistor or synchronized to an external signal. The brightness is controlled by an analog voltage on the CNTL pin. The device directly 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
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Ordering Information
PART MAX8722CEEG TEMP RANGE -40°C to +85°C PIN-PACKAGE 24 QSOP PKG CODE E24-1
Pin Configuration
VIN
Minimal Operating Circuit
VCC BATT GND VDD
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 24 GND 23 VCC 22 VDD 21 PGND
VCC VCC BST2 BST1 GH1 ILIM
MAX8722C
20 GL2 19 GL1 18 GH1 17 LX1 16 BST1 15 BST2 14 LX2 13 GH2
MAX8722C LX1
LX2 FREQ GL1
PGND SHDN CNTL SYNC DPWM COMP TFLT GL2 GH2 VFB ISEC IFB
QSOP ________________________________________________________________ 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.
Low-Cost CCFL Backlight Controller MAX8722C
ABSOLUTE MAXIMUM RATINGS
BATT to GND..........................................................-0.3V to +30V BST1, BST2 to GND................................................-0.3V to +36V BST1 to LX1, BST2 to LX2 ........................................-0.3V to +6V CNTL, FREQ, SYNC, VCC, VDD to GND ...................-0.3V to +6V COMP, DPWM, ILIM, TFLT to GND.............-0.3V to (VCC + 0.3V) GH1 to LX1 ..............................................-0.3V to (VBST1 + 0.3V) GH2 to LX2 ..............................................-0.3V to (VBST2 + 0.3V) GL1, GL2 to GND .......................................-0.3V to (VDD + 0.3V) IFB, ISEC, VFB to GND................................................-3V to +6V SHDN to GND...........................................................-0.3V to +6V PGND to GND........................................................-0.3V to +0.3V Continuous Power Dissipation (TA = +70°C) 24-Pin QSOP (derate 9.5mW/°C above +70°C)........761.9mW Operating Temperature Range ............................-40°C to +85°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°C Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1. VBATT = 12V, VCC = VDD, V SHDN = 5.4V, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.)
PARAMETER BATT Input Voltage Range BATT Quiescent Current BATT Quiescent Current, Shutdown VCC Output Voltage, Normal Operation VCC Output Voltage, Shutdown VCC Undervoltage-Lockout Threshold (VUVLO) www.DataSheet4U.com VCC Undervoltage-Lockout Hysteresis GH1, GH2, GL1, GL2 OnResistance, High GH1, GH2, GL1, GL2 OnResistance, Low GH1, GH2, GL1, GL2 Maximum Output Current BST1, BST2 Leakage Current Resonant Frequency Ra.