MAX8728 19-3910 Rev 0 1/06 Low-Cost, Multiple-Output Power Supply for LCD Monitors/TVs General Description Features Optimized for 10.8V to 13.2V Input Supply The MAX8728 generates all the supply rails for thin-film transistor (TFT) liquid-crystal display (LCD) panels in TVs 7V to 13.2V Input Supply Range and monitors. It includes step-down and step-up regula- Selectable Frequency (500kHz/1MHz/1.5MHz) tors, positive and negative charge pumps, and a dual- Current-Mode Step-Down Regulator mode, logic-controlled high-voltage switch control block. 14V Internal n-Channel MOSFET The MAX8728 can operate from input voltages from 7V to 13.2V and is optimized for LCD TV panel and LCD moni- 1.5% Accurate Output tor applications running directly from 12V supplies. Current-Mode Step-Up Regulator The step-up and step-down regulators feature internal 19V Internal n-Channel MOSFET power MOSFETs and high-frequency operation allow- 1% Accurate Output ing the use of small inductors and capacitors, resulting True Shutdown (Output Goes to Zero) in a compact solution. Both switching regulators use 180 Out-of-Phase Switching fixed-frequency, current-mode control architectures, Adjustable Positive/Negative Charge Pumps providing fast load-transient response and easy com- pensation. The positive and negative charge-pump reg- Soft-Start and Timer Delay Fault Latch for All ulators provide TFT gate-driver supply voltages. Both Outputs output voltages can be adjusted with external resistive Logic-Controlled, High-Voltage Switches voltage-dividers. Power-Up and Power-Down Sequences The MAX8728 is available in a small (5mm x 5mm), low- Thermal-Overload Protection profile (0.8mm), 32-pin TQFN package and operates over the -40C to +85C temperature range. Simplified Operating Circuit Applications LCD Monitors LCD TVs AV V DD IN Ordering Information V L INL GATE LX2 V L PIN- PACKAGE GND2 PART TEMP RANGE PACKAGE CODE FB2 BST COMP 32 TQFN-EP* MAX8728ETJ+ -40C to +85C T3255-4 IN 5mm x 5mm OUT1 LX1 SHDN ON/OFF +Denotes lead-free package. EN LCD ENABLE DEL *EP = Exposed pad. GND1 Pin Configuration OUT1 MAX8728 CTL FROM T CON THR TOP VIEW MODE FBI FSEL 24 23 22 21 20 19 18 17 16 GND2 25 DRVP DRN V V VL CC GON 15 GNDP LX2 26 GON REF SRC 14 FBP GATE 27 13 REF EN 28 GND MAX8728 29 12 MODE GND FBN FBP 30 11 SHDN DEL DRVN SUPP DRVP 31 10 V COMP CC V GOFF 32 9 VL FB1 V IN 12 3 45 6 7 8 TQFN True Shutdown is a trademark of Maxim Integrated Products, Inc. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLE GND1 FBN OUT1 FB2 DRVN THR CTL DRN IN GON LX1 SRC BST FSEL INL SUPPLow-Cost, Multiple-Output Power Supply for LCD Monitors/TVs ABSOLUTE MAXIMUM RATINGS IN, INL, SUPP to GND ............................................-0.3V to +14V SRC to DRN............................................................-0.3V to +40V SUPP to IN ..........................................................................0.3V DRN to GND...........................................................-0.3V to +40V DRVP to GNDP.........................................-0.3V to V + 0.3V GON to DRN...........................................................-0.3V to +30V SUPP CTL, EN, SHDN, OUT1, V , V to GND ................-0.3V to +6V V Short Circuit to GND..............................................Momentary L CC L COMP, FB1, FB2, FBN, FBP, FSEL, DEL, REF Short Circuit to GND...........................................Continuous THR, MODE, REF to GND........................-0.3V to V + 0.3V DRVN RMS Current..........................................................-400mA CC GND1, GND2, GNDP to GND.............................................0.3V DRVP RMS Current.........................................................+100mA BST to GND1..........................................................-0.3V to +20V LX2 RMS Current................................................................+1.6A LX1 to BST................................................................-6V to +0.3V GND2 RMS Current ............................................................+1.6A LX2 to GND2 ..........................................................-0.3V to +19V LX1 RMS Current .................................................................-1.6A DRVN, LX1, GATE to GND1 ..........................-0.3V to V + 0.3V Continuous Power Dissipation (T = +70C) A IN GON, SRC to GND .................................................-0.3V to +40V 32-Pin Thin QFN (derate 34.5mW/C above +70C).....2758mW SRC to GON ...........................................................-0.3V to +40V Operating Temperature Range ...........................-40C to +85C SRC to SUPP ..........................................................-0.3V to +30V Junction Temperature......................................................+150C SRC to SUPP (momentary)......................................-14V to +30V Storage Temperature Range .............................-65C to +160C GON to SUPP ..........................................................-14V to +30V Lead Temperature (soldering, 10s) .................................+300C 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 = V = V = 12V, V = +3.3V, V = 28V, GND1 = GND2 = GNDP = GND = 0, I = 0, T = 0C IN INL SUPP OUT1 SRC REF A to +85C. Typical values are at T = +25C, unless otherwise noted.) A PARAMETER CONDITIONS MIN TYP MAX UNITS GENERAL IN, INL Input Voltage Range For VL regulator operation 7.0 12.0 13.2 V V = V = 2.2V, V = 0, FB2 FBP FBN INL Quiescent Current 7mA LX2 not switching, LX1 switching IN Standby Supply Current V = 7V to 13.2V, EN = SHDN = GND 0.5 mA IN FSEL = GND 1275 1500 1730 Switching Frequency FSEL = V 850 1000 1150 kHz CC FSEL = REF 425 530 610 Phase Difference Between Step-Down/Positive and 180 Degrees Step-Up/Negative Regulators VL REGULATOR 7V < V < 13.2V, V = V = V = INL FB1 FB2 FBP VL Output Voltage 4.8 5.0 5.1 V 1.9V, V = 0.5V, I = 25mA FBN VL VL Undervoltage Lockout VL rising, 2.5% hysteresis 3.8 4.0 4.1 V Threshold REFERENCE REF Output Voltage No external load 1.98 2.00 2.02 V REF Load Regulation 0 < I < 50A 10 mV REF REF Sink Current REF in regulation 0 10 A REF Undervoltage Lockout Rising edge, 200mV hysteresis 1.5 V Threshold 2 MAX8728