LT1942

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Quad DC/DC Converter for Triple Output TFT Supply Plus LED Driver

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Overview

  • Triple Output TFT Supply with Built-In Power Sequencing
  • Integrated White LED Backlight Driver
  • Integrated Schottky Diodes
  • Active Ballast Circuitry Ensures Precise Current Matching in White LEDs
  • Low Noise 1MHz Fixed Frequency Operation
  • 2.6V to 16V Input Voltage Range
  • Soft-Start Limits Inrush Current
  • TFT Supply Output Voltages Independently Set (Not Charge Pump Derived)
  • Power Good and Output Disconnect for TFT Supply
  • Built-In LED Dimming Capability
  • Open LED Protection for LED Driver
  • 24-Lead QFN Package (4mm × 4mm)

The LT1942 is a highly integrated quad switching regulator designed to provide all necessary power supply functions for TFT displays, including the white LED backlight driver. The TFT supply incorporates two boost and one inverting DC/DC converters. The TFT supply output voltages are independently set, unlike charge pump solutions which have many limitations. Power sequencing for the TFT supply is built into the part and is user programmable.

The LED driver is a boost DC/DC converter that can be independently controlled. The LED driver has built-in dimming control for precise control of LED current. An 8:1 dimming range is achieved by adjusting the CTRL4 voltage. The user can elect to drive a single string or two strings of LEDs. An LED ballast circuit is included to precisely match the LED currents if two strings of LEDs are used. Soft-start is built into the LED driver as well as the primary TFT supply.

The LT1942 is available in a low profile (0.75mm) 24-lead QFN (4mm × 4mm) package.

Applications

  • Poly-Silicon TFT Displays
  • Amorphous Silicon TFT Displays
LT1942
Quad DC/DC Converter for Triple Output TFT Supply Plus LED Driver
TFT Bias and White LED Backlight Power Supply Product Package 1
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Documentation

Data Sheet 1

Reliability Data 1

User Guide 1

Technical Articles 1

Data Sheet

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Evaluation Kits

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schematic 1
DC688A

LT1942EUF | Quad Converter For TFT Supply and LED Driver, VIN=3V-4.5V, VON=10V/2mA, VOFF=-10V/2mA, AVDD=5V/40mA

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Product Details

Demonstration Circuit DC688 is a quad output power supply intended for use in small to medium size TFT panels. The circuit features the LT1942 quad output switching regulator and generates an LED driver along with the triple output supply required for the TFT panels. With an input voltage range of 3V to 4.2V, two step-up regulators and one inverting regulator provide AVDD , VON and VOFF bias voltages for the LCD panels. Another high power boost is used to drive 12 LEDs (2 strings of 6 LEDs each). For 3V minimum input voltage, up to 20mA current is available for each LED string. A built-in LED ballast circuit is included to precisely match the LED currents in the two strings.


 
DC688A
LT1942EUF | Quad Converter For TFT Supply and LED Driver, VIN=3V-4.5V, VON=10V/2mA, VOFF=-10V/2mA, AVDD=5V/40mA
DC688A - Schematic

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