EVALUATION KIT AVAILABLE MAX8729 Constant-Frequency, Half-Bridge CCFL Inverter Controller General Description Features The MAX8729 cold-cathode-fluorescent lamp (CCFL) Low-Cost, Half-Bridge Inverter Topology inverter controller is designed to drive multiple CCFLs Resonant Mode Striking Ensures Startup using the half-bridge inverter consisting of two external Constant-Frequency Operation After Lamp Ignition n-channel power MOSFETs. The half-bridge topology Drives Large External MOSFETs minimizes the component count, while providing near Supports Multilamp Applications sinusoidal drive waveforms. The MAX8729 operates in resonant mode during striking and switches over to Sync and Phase-Shift Controls Allow Daisy- Chained constant-frequency operation after all the lamps are lit. Operation This unique feature ensures reliable striking under all Adjustable Switching Frequency and DPWM conditions and reduces the transformer stress. Frequency The MAX8729 provides accurate lamp-current regulation 2.5% Lamp-Current Regulation (2.5%). The lamp current is adjustable with an external 10:1 Dimming Range resistor. The MAX8729 changes the brightness by turning the CCFL on and off using a digital pulse-width modul- Accurate Analog-Dimming Control tion (DPWM) method, while maintaining the lamp current Lamp-Out Detection with Adjustable Timeout constant. The brightness can be adjusted with an analog Secondary Current and Voltage Limiting voltage on the CNTL pin, or with an external PWM signal. Primary Current Limit with R Sensing DS(ON) The MAX8729 is capable of synchronizing and adjusting Adjustable DPWM Rise and Fall Time the phase of the gate drivers and DPWM oscillator. These features allow multiple MAX8729 ICs to be connected in Low-Cost, 28-Pin QSOP Package a daisy-chain configuration. The switching frequency and DPWM frequency of the master IC can be easily adjusted Simplified Operating Circuit using external resistors, or synchronized with system INPUT signals. If the controller loses the external sync signals, it VCC switches over to the internal oscillators and keeps opera ing. Phase-shift select pins PS1 and PS2 can be used 3 28 IN V DD 5 to program four different phase shifts, allowing up to five GND 4 25 V BST MAX8729s to be used together. VCC CC 24 GH ON/OFF The MAX8729 protects the inverter from lamp-out, sec- 8 SHDN ondary overvoltage, and secondary short-circuit faults. 23 DIMMING LX 7 CNTL The MAX8729 can drive large-power MOSFETs typically 2 SEL 27 used in applications where one power stage drives four GL 12 26 PSCK PGND or more CCFL tubes in parallel. An internal 5.35V linear CCFL regulator powers the MOSFET drivers and most of the 22 19 PS1 VFB 20 internal circuitry. The MAX8729 is available in a low-cost, ISEC 16 PS2 18 28-pin QSOP package and operates over the -40C to IFB 15 17 HF COMP +85C extended temperature range. MAX8729 Applications 9 6 TFLT LF LCD Monitors Notebook Computers LCD TVs 11 DPWM 1 PCOMP Ordering Information 13 14 HFCK HSYNC PART TEMP RANGE PIN-PACKAGE 10 21 LFCK LSYNC MAX8729EEI -40C to +85C 28 QSOP Pin Configuration appears at end of data sheet. 19-3754 Rev 1 4/14MAX8729 Constant-Frequency, Half-Bridge CCFL Inverter Controller Absolute Maximum Ratings IN, LX to GND .......................................................-0.3V to +30V SHDN to GND .........................................................-0.3V to +6V BST to GND ..........................................................-0.3V to +36V PGND to GND ......................................................-0.3V to +0.3V BST to LX ................................................................-0.3V to +6V Continuous Power Dissipation (T = +70C) A V , V to GND ...................................................-0.3V to +6V 28-Pin QSOP (derate 10.8mW/C above +70C) ....860.2mW CC DD GH to LX....................................................-0.3V to V + 0.3V Operating Temperature Range ........................... -40C to +85C BST CNTL, COMP, GL, DPWM, HF, LF, HFCK, Junction Temperature ......................................................+150C LFCK, HSYNC, LSYNC, PS1, PS2, PSCK, TFLT, Storage Temperature Range ............................ -65C to +150C PCOMP, SEL ...........................................-0.3V to V + 0.3V Lead Temperature (soldering, 10s) .................................+300C CC IFB, ISEC, VFB to GND .............................................-6V 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 (V = 12V, V = 5.3V, T = 0C to +85C, unless otherwise noted. Typical values are at T = +25C.) IN DD A A PARAMETER CONDITIONS MIN TYP MAX UNITS IN Input Voltage Range 6 28 V IN Quiescent Current V = 5.3V, V = 28V 3.2 6 mA SHDN IN IN Quiescent Current, Shutdown 6 20 A SHDN = GND V Output Voltage, Normal V = 5.3V, 6V < V < 28V, CC SHDN IN 5.20 5.35 5.50 V Operation 0 < I < 10mA LOAD V Output Voltage, Shutdown 3.5 4.6 5.5 V SHDN = GND, no load CC V rising (leaving lockout) 4.5 V Undervoltage CC CC V Lockout Threshold V falling (entering lockout) 4.0 CC V Undervoltage-Lockout CC 200 mV Hysteresis GH, GL On-Resistance, Low State I = 10mA 1 2 TEST GH, GL On-Resistance, High State I = 10mA 4 6 TEST BST Leakage Current V = 17V, V = 12V 5 A BST LX Resonant Frequency Range Not tested 30 80 kHz Minimum Off-Time 330 416 560 ns Maximum Off-Time (LX-GND) 24.0 30.7 42.0 s Low-Side MOSFET Maximum Current- 370 400 470 mV Limit Threshold (LX-GND) High-Side MOSFET Maximum 370 400 470 mV Current-Limit Threshold (IN LX) Low-Side MOSFET Zero-Current- 0 10 18 mV Crossing Threshold (GND LX) High-Side MOSFET Zero-Current- -16 +6 +28 mV Crossing Threshold (LX IN) Current-Limit Leading Edge Blanking 310 410 560 ns IFB Regulation Point Internally full-wave rectified 770 790 810 mV IFB Maximum AC Voltage 3 V Maxim Integrated 2 www.maximintegrated.com