Analog Devices

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.ApplicationsPoly-Silicon TFT DisplaysAmorphous Silicon TFT Displays

The LT1943 quad output adjustable switching regulator provides power for large TFT LCD panels. The device, housed in a low profile 28 pin thermally enhanced TSSOP package, can generate a 3.3V or 5V logic supply along with the triple output supply required for the TFT LCD panel. Operating from an input range of 4.5V to 22V, a step-down regulator provides a low voltage output VLOGICwith up to 2A current. A high-power step-up converter, a lowerpower step-up converter and an inverting converter provide the three independent output voltages AVDD, VONand VOFFrequired by the LCD panel. A high-side PNP provides delayed turn-on of the VONsignal and can handle up to 30mA. Protection circuitry ensures that VONis disabled if any of the four outputs are more than 10% below the programmed voltage.All switchers are synchronized to an internal 1.2MHz clock, allowing the use of low profile inductors and ceramic capacitors throughout. A current mode architecture provides excellent transient response. For best flexibility, all outputs are adjustable. Soft-start is included in all four channels. APGOODpin can drive an optional PMOS pass device to provide output disconnect for the AVDDoutput.ApplicationsLarge TFT-LCD Desktop MonitorsFlat Panel Televisions

The LT1944 is a dual micropower step-up DC/DC converter in a 10-pin MSOP package. Each converter is designed with a 350mA current limit and an input voltage range of 1.2V to 15V, making the LT1944 ideal for a wide variety of applications. Both converters feature a quiescent current of only 20µA at no load, which further reduces to 0.5µA in shutdown. A current limited, fixed off-time control scheme conserves operating current, resulting in high efficiency over a broad range of load current. The 36V switch allows high voltage outputs up to 34V to be easily generated in a simple boost topology without the use of costlt transformers. The LT1944's low off-time of 400ns permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications.Switch CurrentLT1944350mA, 350mALT1944-1100mA, 175mAApplicationsLCD BiasHandheld ComputersBattery BackupDigital Cameras

The LT1945 is a dual micropower DC/DC converter in a 10-pin MSOP package. Each converter is designed with a 350mA current limit and an input voltage range of 1.2V to 15V, making the LT1945 ideal for a wide variety of applications. Both converters feature a quiescent current of only 20µA at no load, which further reduces to 0.5µA in shutdown. A current limited, fixed off-time control scheme conserves operating current, resulting in high efficiency over a broad range of load current. The 36V switch allows high voltage outputs up to ±34V to be easily generated without the use of costly transformers. The LT1945’s low off-time of 400ns permits the use of tiny, low profile inductors and capacitors to minimize footprint and cost in space-conscious portable applications.ApplicationsSmall TFT LCD PanelsHandheld ComputersBattery BackupDigital Cameras

The LT1946 is a fixed frequency step-up DC/DC converter containing an internal 1.5A, 36V switch. Capable of generating 8V at 430mA from a 3.3V input, the LT1946 is ideal for large TFT-LCD panel power supplies. The LT1946 switches at 1.2MHz, allowing the use of tiny, low profile inductors and low value ceramic capacitors. Loop compensation can be either internal or external, giving the user flexibility in setting loop compensation and allowing optimized transient response with low ESR ceramic output capacitors. Soft-start is controlled with an external capacitor, which determines the input current ramp rate during start-up.The 8-lead MSOP package and high switching frequency ensure a low profile overall solution less than 1.2mm high.Switching FrequencyLT19461.2MHzLT1946A2.7MHzApplicationsTFT-LCD Bias SuppliesGPS ReceiversDSL ModemsLocal Power Supplies

The LT1947 is a highly integrated multiple output DC/DC converter designed for use in TFT-LCD panels. The device contains two independent switching regulators. The main regulator has an adjustable output voltage with an internal 1.1A switch that can generate a boosted voltage as high as 30V. The second regulator’s output is also adjustable up to 30V and can deliver 10mA for positive bias. A simple level-shift charge pump off the main switch node generates the negative bias voltage. An external capacitor sets the delay time from AVDD’s final value to the rising edge at the VONpin. The 3MHz switching frequency allows the use of tiny low profile chip inductors and capacitors throughout, providing a low noise, low cost total solution with all components under 1.2mm in height. The device operates from an input range of 2.7V to 8V and is available in 10-lead MSOP and thermally enhanced 10-lead MSOP packages.ApplicationsTFT-LCD Notebook Display PanelsTFT-LCD Desktop Monitor Display PanelsDigital CamerasHandheld Computers

The LT1949 is a fixed frequency step-up DC/DC converter with a 1A, 0.5Ω internal switch. Capable of generating 10V at 175mA from a 3.3V input, the LT1949 is ideal for generating bias voltages for large screen LCD panels. Constant frequency 600kHz operation results in a low noise output that is easy to filter and the 30V switch rating allows output voltage up to 28V using a single inductor. An external compensation pin gives the user flexibility in optimizing loop compensation, allowing small low ESR ceramic capacitors to be used at the output. The 8-lead MSOP and SO packages ensure a low profile overall solution.The LT1949 includes a low-battery detector that stays alive when the device goes into shutdown. Quiescent current in shutdown is 25µA, while operating current is 4.5mA.ApplicationsLCD Bias SuppliesGPS ReceiversBattery BackupPortable Electronic EquipmentDiagnostic Medical Instrumentation

The LT1950 is a wide input range, forward, boost, flyback and SEPIC controller that drives an N-channel power MOSFET with few external components required.A resistor programmable duty cycle clamp can be used to generate a volt-second clamp for forward converter applications. An internal boost switcher is available for creating a separate supply for the output gate driver, allowing 10V gate drive from input voltages as low as 3V. The LT1950’s operating frequency can be set with an external resistor over a 100kHz to 500kHz range and a SYNC pin allows the part to be synchronized to an external clock. Additional programmability exists for leading edge blanking and slope compensation.A fast current sense comparator achieves 60ns current sense delay and the error amplifier is a true voltage mode error amplifier, allowing a wide range of compensation networks. An accurate shutdown pin with programmable hysteresis is available for undervoltage lockout and shutdown. The LT1950 is available in a small 16-Pin SSOP package.ApplicationsTelecom Power SuppliesAutomotive Power SuppliesPortable Electronic EquipmentIsolated and Nonisolated DC/DC Converters

The LT1952/LT1952-1 are current mode PWM controllers optimized to control the forward converter topology, using one primary MOSFET. The LT1952/LT1952-1 provide synchronous rectifier control, resulting in extremely high efficiency. A programmable Volt-Second clamp provides a safeguard for transformer reset that prevents saturation. This allows a single MOSFET on the primary side to reliably run at greater than 50% duty cycle for high MOSFET, transformer and rectifier utilization. The devices include soft-start for controlled exit from shutdown and undervoltage lockout. A precision 107mV current limit threshold, independent of duty cycle, combines with softstart to provide hiccup short circuit protection. The LT1952 is optimized for micropower bootstrap startup from high input voltages. The LT1952-1 allows startup from lower input voltages. Programmable slope compensation and leading edge blanking allow optimization of loop bandwidth with a wide range of inductors and MOSFETs. Each device can be programmed over a 100kHz to 500kHz frequency range and the part can be synchronized to an external clock. The error amplifier is a true op amp, allowing a wide range of compensation networks. The LT1952/LT1952-1 are available in a small 16-pin SSOP package.ApplicationsTelecommunications Power SuppliesIndustrial and Distributed PowerIsolated and Non-Isolated DC/DC Converters

The LT1956/LT1956-5 are 500kHz monolithic buck switching regulators with an input voltage capability up to 60V. A high efficiency 1.5A, 0.2Ω switch is included on the die along with all the necessary oscillator, control and logic circuitry. A current mode architecture provides fast transient response and good loop stability.Special design techniques and a new high voltage process achieve high efficiency over a wide input range. Efficiency is maintained over a wide output current range by using the output to bias the circuitry and by utilizing a supply boost capacitor to saturate the power switch. Patented circuitry maintains peak switch current over the full duty cycle range*. A shutdown pin reduces supply current to 25µA and the device can be externally synchronized from 580kHz to 700kHz with a logic level input.The LT1956/LT1956-5 are available in fused-lead 16-pin SSOP and thermally enhanced TSSOP packages.ApplicationsHigh Voltage, Industrial and AutomotivePortable ComputersBattery-Powered SystemsBattery ChargersDistributed Power Systems