LT1942 Quad DC/DC Converter for Triple Output TFT Supply Plus LED Driver FEATURES DESCRIPTIO Triple Output TFT Supply with Built-In The LT 1942 is a highly integrated quad switching regu- Power Sequencing lator designed to provide all necessary power supply Integrated White LED Backlight Driver functions for TFT displays, including the white LED Integrated Schottky Diodes backlight driver. The TFT supply incorporates two boost Active Ballast Circuitry Ensures Precise Current and one inverting DC/DC converters. The TFT supply Matching in White LEDs output voltages are independently set, unlike charge Low Noise 1MHz Fixed Frequency Operation pump solutions which have many limitations. Power 2.6V to 16V Input Voltage Range sequencing for the TFT supply is built into the part and is Soft-Start Limits Inrush Current user programmable. TFT Supply Output Voltages Independently Set The LED driver is a boost DC/DC converter that can be (Not Charge Pump Derived) independently controlled. The LED driver has built-in Power Good and Output Disconnect for TFT Supply dimming control for precise control of LED current. An 8:1 Built-In LED Dimming Capability dimming range is achieved by adjusting the CTRL4 volt- Open LED Protection for LED Driver age. The user can elect to drive a single string or two 24-Lead QFN Package (4mm 4mm) strings of LEDs. An LED ballast circuit is included to U precisely match the LED currents if two strings of LEDs are APPLICATIO S used. Soft-start is built into the LED driver as well as the primary TFT supply. Poly-Silicon TFT Displays Amorphous Silicon TFT Displays The LT1942 is available in a low profile (0.75mm) 24-lead , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. QFN (4mm 4mm) package. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO TFT Bias and White LED Backlight Power Supply CMDSH-3 22H AV Si2301BDS DD V IN 5V 3V TO 4.2V 22H 40mA 2.2F 301k 4.7pF 1M 698k D3 SW3 V SW1 CC V 0.22F 4.7F ON FB3 FB1 100k 20mA 20mA 4.7F 10V 100k PGND14 2mA PGND23 PGOOD 10k V SW4 V IN OUT3 LT1942 33H 0.22F NFB2 D4 665k D2 LED1 47H V OFF 0.1F 10V SW2 LED2 2mA 47H SHDN FB4 SGND/ V IN CTRL4 AGND SS1 SS4 CT SHUTDOWN 1942 TA01 4.99 0.1F 0.1F LED CONTROL 0.1F 1942fb 1 U ULT1942 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART V Voltage............................................................. 16V CC NUMBER SW1, SW2, SW3 Voltage .......................... 0.4V to 36V SW4.......................................................... 0.4V to 45V LT1942EUF 24 23 22 21 20 19 FB1, FB3 Voltage ................................................... 2.5V PGND23 1 18 LED1 FB4 Voltage ....................................................... 400mV SW3 2 17 LED2 NFB2 Voltage ................................................... 200mV D3 3 16 D4 25 SHDN Voltage ......................................................... 10V V 4 15 FB4 OUT3 CTRL4 Voltage ........................................................ 16V FB3 5 14 FB1 UF PART NFB2 6 13 PGOOD SS1, SS4 Voltage .................................................. 1.5V MARKING Current Into D2 ......................................................... 1A 7 8 9 10 11 12 1942 D2 Voltage ............................................................ 36V Current Out of D3 ..................................................... 1A UF PACKAGE D3 Voltage .............................................................. 36V 24-LEAD (4mm 4mm) PLASTIC QFN T = 125C, = 37C/W, = 4.3C/W JMAX JA JC Current Out of D4 ..................................................... 4A EXPOSED PAD (PIN 25) IS SGND (MUST BE SOLDERED TO PCB) D4 Voltage .............................................................. 45V LED1, LED2 Voltage ............................................... 45V Order Options Tape and Reel: Add TR Current Into LED1, LED2 ..................................... 35mA Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: