LT1943 High Current Quad Output Regulator for TFT LCD Panels FEATURES DESCRIPTIO The LT 1943 quad output adjustable switching regulator 4 Integrated Switches: 2.4A Buck, 2.6A Boost, provides power for large TFT LCD panels. The device, 0.35A Boost, 0.35A Inverter (Guaranteed Minimum housed in a low profile 28 pin thermally enhanced TSSOP Current Limit) package, can generate a 3.3V or 5V logic supply along with Fixed Frequency, Low Noise Outputs the triple output supply required for the TFT LCD panel. Soft-Start for all Outputs Operating from an input range of 4.5V to 22V, a step-down Externally Programmable V Delay ON regulator provides a low voltage output V with up to LOGIC Integrated Schottky Diode for V Output ON 2A current. A high-power step-up converter, a lower- PGOOD Pin for AV Output Disconnect DD power step-up converter and an inverting converter pro- 4.5V to 22V Input Voltage Range vide the three independent output voltages AV , V and DD ON TM PanelProtect Circuitry Disables V Upon Fault ON V required by the LCD panel. A high-side PNP provides OFF Available in Thermally Enhanced 28-Lead TSSOP delayed turn-on of the V signal and can handle up to ON U 30mA. Protection circuitry ensures that V is disabled if ON APPLICATIO S any of the four outputs are more than 10% below the programmed voltage. Large TFT-LCD Desktop Monitors All switchers are synchronized to an internal 1.2MHz Flat Panel Televisions clock, allowing the use of low profile inductors and ce- , LTC and LT are registered trademarks of Linear Technology Corporation. ramic capacitors throughout. A current mode architecture PanelProtect is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. provides excellent transient response. For best flexibility, all outputs are adjustable. Soft-start is included in all four channels. A PGOOD pin can drive an optional PMOS pass device to provide output disconnect for the AV output. DD TYPICAL APPLICATIO V 8V TO 20V IN, 10H V AV OFF DD 5.5V 12.2V 50mA 500mA 1F 0.47F 10F 33H 10H 88.7k 10F 2.2F Startup Waveforms 44.2k V SW3 IN SW4 SW2 RUN-SS 10.0k NFB4 FB2 2V/DIV 0.015F V RUN-SS LOGIC 10.0k 10pF 10H 0.015F 5V/DIV SS-234 0.047F AV LT1943 DD FB4 C T 10V/DIV BIAS PGOOD PGOOD V ON V OFF BOOST V 35V ON 10V/DIV 30mA 0.22F E3 SW1 274k V E3 4.7H 20V/DIV 16.2k FB3 V LOGIC V ON FB1 GND 10.0k 3.3V 50V/DIV 2A SGND V 10.0k C1 I IN(AVG) V V V C2 C3 C4 2.2F 1A/DIV 22F 5ms/DIV 0.47F 18k 13k 6.8k 27k 100pF 100pF 100pF 100pF 2.2nF 2.2nF 2.2nF 680pF 1943 TA01 Quad Output TFT-LCD Power Supply 1943fa 1 U ULT1943 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) ORDER PART TOP VIEW V Voltage .............................................................. 25V IN NUMBER GND 1 28 SW2 BOOST Voltage ........................................................ 36V VC1 2 27 SW2 BOOST Voltage Above SW1 ..................................... 25V LT1943EFE VC2 3 26 V ON FB1 4 25 C BIAS Pin Voltage ..................................................... 18V T FB2 5 24 E3 SW2, SW4 Pin Voltages .......................................... 40V FB3 6 23 PGOOD SW3 Voltage ............................................................ 40V NFB4 7 BIAS 22 29 FB4 8 21 SW3 FB1, FB2, FB3, FB4 Voltages...................................... 4V VC3 9 GND 20 NFB4 Voltage ................................................ +6V, 0.6V VC4 10 19 SW4 VC1, VC2, VC3, VC4 Pin Voltages .............................. 6V SGND 11 18 RUN-SS FE PART MARKING BOOST 12 17 SS-234 RUN-SS, SS-234 Pin Voltages................................... 6V SW1 13 16 V IN 1943E PGOOD Pin Voltage ................................................. 36V SW1 14 15 V IN E3 Pin Voltage ......................................................... 38V FE PACKAGE V Voltage ............................................................. 38V 28-LEAD PLASTIC TSSOP ON EXPOSED PAD (PIN 29) IS GROUND C Pin Voltage ........................................................... 6V T (MUST BE SOLDERED TO PCB) Junction Temperature........................................... 125C T = 125C, = 25C/W, = 7.5C/W JMAX JA JC Operating Temperature Range (Note 2) ...40C to 85C Storage Temperature Range ..................65C to 150C Consult LTC Marketing for parts specified with wider operating temperature ranges. Lead Temperature (Soldering, 10 sec).................. 300C ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25C. V = 12V, RUN-SS, SS-234 = 2.5V unless otherwise noted. A IN PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage 4.5 V Maximum Input Voltage 22 V Quiescent Current Not Switching 10 14 mA RUN-SS = SS-234 = 0V 35 45 A RUN-SS, SS-234 Pin Current RUN-SS, SS-234 = 0.4V 1.7 A RUN-SS, SS-234 Threshold 0.8 V BIAS Pin Voltage to Begin SS-234 Charge 2.4 2.8 3.15 V BIAS Pin Current BIAS = 3.1V, All Switches Off 10.5 15 mA FB Threshold Offset to Begin C Charge (Note 3) 90 125 160 mV T C Pin Current Source All FB Pins = 1.5V 16 20 25 A T C Threshold to Power V All FB Pins = 1.5V 1.0 1.1 1.2 V T ON V Switch Drop V Current = 30mA 180 240 mV ON ON Maximum V Current V = 30V 30 60 mA ON E3 PGOOD Threshold Offset 90 125 160 mV PGOOD Sink Current 200 A PGOOD Pin Leakage V = 36V 1 A PGOOD Master Oscillator Frequency 1.1 1.2 1.35 MHz 1.0 1.46 MHz Foldback Switching Frequency All FB Pins = 0V 250 kHz Frequency Shift Threshold on FB 200kHz 0.5 V 1943fa 2 U WWW