MAX8722A 19-3321 Rev 0 10/05 Low-Cost CCFL Backlight Controller General Description Features The MAX8722A integrated backlight controller is opti- Synchronized to Resonant Frequency mized to drive cold-cathode fluorescent lamps (CCFLs) Longer Lamp Life using a full-bridge resonant inverter architecture. Guaranteed Striking Capability Resonant operation maximizes striking capability and High Power to Light Efficiency provides near-sinusoidal waveforms over the entire Wide Input Voltage Range (4.6V to 28V) input range to improve CCFL lifetime. The controller Input-Voltage Feed-Forward for Excellent Line operates over a wide input voltage range (4.6V to 28V) Rejection with high power to light efficiency. The device also includes safety features that effectively protect against Accurate Dimming Control with Analog Interface many single-point fault conditions including lamp-out 10:1 Dimming Range and short-circuit faults. Adjustable Accurate DPWM Frequency with Sync The MAX8722A achieves 10:1 dimming range by chop- Function ping the lamp current on and off using a digital pulse- Adjustable Lamp Current Rise and Fall Time width modulation (DPWM) method. The DPWM frequency can be accurately adjusted with a resistor or synchro- Secondary Voltage Limit Reduces Transformer nized to an external signal. The brightness is controlled Stress by an analog voltage on the CNTL pin. The device direct- Lamp-Out Protection with Adjustable Timeout ly drives the four external n-channel power MOSFETs of Secondary Overcurrent Protection with the full-bridge inverter. An internal 5.3V linear regulator Adjustable Timeout powers the MOSFET drivers, the DPWM oscillator, and most of the internal circuitry. The MAX8722A is available Low-Cost 24-Pin QSOP Package in a low-cost, 24-pin QSOP package and operates over a -40C to +85C temperature range. Ordering Information Applications PKG PART TEMP RANGE PIN-PACKAGE CODE Notebook Computer Displays 24 QSOP MAX8722AEEG -40C to +85C E24-1 LCD Monitors LCD TVs Minimal Operating Circuit V IN V CC Pin Configuration BATT V DD TOP VIEW GND V CC BATT 1 24 GND V CC BST2 SHDN 2 23 V CC BST1 GH1 ILIM 3 22 V DD ILIM TFLT 4 21 PGND MAX8722A LX1 MAX8722A CNTL 5 20 GL2 LX2 DPWM 6 19 GL1 FREQ GL1 SYNC 7 18 GH1 PGND FREQ 8 17 LX1 SHDN GL2 CNTL COMP 9 16 BST1 GH2 SYNC VFB IFB 10 15 BST2 DPWM ISEC COMP IFB VFB 11 14 LX2 TFLT ISEC 12 13 GH2 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 ABSOLUTE MAXIMUM RATINGS BATT to GND..........................................................-0.3V to +30V SHDN to GND...........................................................-0.3V to +6V BST1, BST2 to GND ...............................................-0.3V to +36V PGND to GND .......................................................-0.3V to +0.3V BST1 to LX1, BST2 to LX2........................................-0.3V to +6V Continuous Power Dissipation (T = +70C) A CNTL, FREQ, SYNC, V , V to GND ...................-0.3V to +6V CC DD 24-Pin QSOP (derate 9.5mW/C above +70C)........761.9mW COMP, DPWM, ILIM, TFLT to GND ............-0.3V to (V + 0.3V) Operating Temperature Range ...........................-40C to +85C CC GH1 to LX1 ..............................................-0.3V to (V + 0.3V) Junction Temperature......................................................+150C BST1 GH2 to LX2 ..............................................-0.3V to (V + 0.3V) BST2 Storage Temperature Range .............................-65C to +150C GL1, GL2 to GND .......................................-0.3V to (V + 0.3V) Lead Temperature (soldering, 10s) .................................+300C DD IFB, ISEC, VFB to GND................................................-3V to +6V 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. V = 12V, V = V , V = 5.3V, T = 0C to +85C. Typical values are at T = +25C, unless otherwise noted.) BATT CC DD SHDN A A PARAMETER CONDITIONS MIN TYP MAX UNITS V = V = V 4.6 5.5 CC DD BATT BATT Input Voltage Range V V = V = open 5.5 28.0 CC DD V = 28V 1 2 BATT BATT Quiescent Current V = V , V = 1V mA SHDN CC IFB V = V = 5V 2 BATT CC BATT Quiescent Current, SHDN = GND 6 20 A Shutdown V Output Voltage, Normal V = 5.5V, 6V < V < 28V, CC SHDN BATT 5.25 5.40 5.55 V Operation 0 < I < 10mA LOAD V Output Voltage, Shutdown SHDN = GND, no load 3.5 4.6 5.5 V CC V rising (leaving lockout) 4.58 V Undervoltage-Lockout CC CC V Threshold V falling (entering lockout) 4.0 CC V Undervoltage-Lockout CC 200 mV Hysteresis GH1, GH2, GL1, GL2 On- I = 10mA, V = V = 5.3V 20 37 TEST CC DD Resistance, High GH1, GH2, GL1, GL2 On- I = 10mA, V = V = 5.3V 10 20 TEST CC DD Resistance, Low GH1, GH2, GL1, GL2 Maximum 0.3 A Output Current BST1, BST2 Leakage Current V = 12V, V = 7V 5 A BST LX Resonant Frequency Range Guaranteed by design 30 80 kHz Minimum Off-Time 340 470 600 ns Maximum Off-Time 24 33 43 s Current-Limit Threshold LX1 to PGND, LX2 to PGND ILIM = V 180 200 220 mV CC (Fixed) Current-Limit Threshold V = 0.5V 80 100 120 ILIM LX1 to PGND, LX2 to PGND mV V = 2.0V 370 400 430 ILIM (Adjustable) 2 MAX8722A