Analog Devices

The LT3484 family of photoflash capacitor charger ICs is designed for use in digital camera and mobile phone applications where space is at a premium. The LT3484's patented control technique allows it to use extremely small transformers, and the improved NPN power switch requires no external Schottky diode clamp, reducing solution size. Output voltage detection requires no external circuitry as the transformer turns ratio determines final charge voltage.The devices feature a VBATpin, which allows the use of 2 alkaline cells to charge the capacitor. The LT3484-0, -2 and -1 have primary current limits of 1.4A, 1A and 0.7A respectively, resulting in tightly controlled average input current of 500mA, 350mA and 225mA respectively. The three versions are otherwise identical.The CHARGE pin gives full control of the part to the user. Driving CHARGE low puts the part in shutdown. TheDONEpin indicates when the part has completed charging. The LT3484 series of parts are housed in a tiny low profile 2mm × 3mm DFN package.ApplicationsDigital Camera and Cell Phone Flash Charger

The LT3485 family of photoflash chargers are highly integrated ICs containing complete charger and IGBT drive functions. The patented control technique of the LT3485-x allows it to use extremely small transformers. Output voltage detection requires no external circuitry. The turns ratio of the transformer controls the final charge voltage. While charging, the output voltage on the capacitor may be monitored by a microcontroller from the monitor pin. Each device contains an on-chip high voltage NPN power switch, which can withstand negative voltages on the switch pin without an external Schottky diode. The device features a VBATpin, which allows the use of two AA cells to charge the capacitor. The internal circuitry operates from the VINpin. The LT3485-0 has a primary current limit of 1.4A, whereas the LT3485-3, LT3485-2, and LT3485-1 have current limits of 2A, 1A and 0.7A respectively. These different current limits result in tightly controlled input currents.The CHARGE pin gives full control of the part to the user. Driving CHARGE low puts the part in shutdown. TheDONEpin indicates when the part has completed charging. The LT3485 series of parts are housed in a leadless (3mm × 3mm) DFN package.ApplicationsDigital Camera and Cell Phone Flash Charger

The LT3486 is a dual step-up DC/DC converter specifically designed to drive up to 16 White LEDs (8 in series per converter) at constant current from a single Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness. The two independent converters are capable of driving asymmetric LED strings.The dimming of the two LED strings can be controlled independently via the respective CTRL pins. An internal dimming system allows the dimming range to be extended up to 1000:1 by feeding a PWM signal to the respective PWM pins. The LT3486 operating frequency can be set with an external resistor over a 200kHz to 2.5MHz range. A low 200mV feedback voltage (±3% accuracy) minimizes power loss in the current setting resistor for better efficiency. Additional features include output voltage limiting when LEDs are disconnected and overtemperature protection.The LT3486 is available in a space saving 16-pin DFN (5mm × 3mm × 0.75mm) and 16-pin thermally enhanced TSSOP packages.ApplicationsNotebook PC DisplayLED Camera Light for Cell PhonesCar Dashboard LightingAvionics Displays

The LT3487 dual channel switching regulator generates positive and negative outputs for biasing CCD imagers. The device delivers up to –8V at 90mA and 15V at 45mA from a lithium-ion cell, providing bias for many popular CCD imagers. The boost regulator incorporates output disconnect technology to eliminate the DC current path from VINto the output load that is present in standard boost configurations. The 2MHz switching frequency allows CCD solutions using tiny, low profile capacitors and inductors and generates low noise outputs that are easy to filter. Schottky diodes are internal and the output voltages are set with one resistor per channel, reducing the external component count.Intelligent soft-start allows sequential soft-start of the two channels with a single capacitor. The soft-start is sequenced such that the output ramp of the negative channel begins after the ramp of the positive channel. Internal sequencing circuitry also disables the negative channel until the positive channel has reached 87% of its final value, ensuring that the sum of the two outputs is always positive.The LT3487 is available in a 10-pin 3mm × 3mm DFN package.ApplicationsCCD BiasTFT LCD BiasOLED Bias±Rail Generation for Op Amps

The LT3489 is a fixed frequency step-up DC/DC converter containing an internal 2.5A, 40V switch. The LT3489 is ideal for large TFT-LCD panel power supplies. The LT3489 switches at 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 MS8E package and high switching frequency ensure a low profile overall solution less than 1.1mm high.ApplicationsTFT-LCD Bias SuppliesGPS ReceiversDSL ModemsLocal Power Supply

The LT3491 is a fixed frequency step-up DC/DC converter specifically designed to drive up to six white LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast resistors. The device features a unique high side LED current sense that enables the part to function as a "one wire current source;" one side of the LED string can be returned to ground anywhere, allowing a simpler one wire LED connection. Traditional LED drivers use a grounded resistor to sense LED current, requiring a 2-wire connection to the LED string.The 2.3MHz switching frequency allows the use of tiny inductors and capacitors. A single pin performs both shutdown and accurate LED dimming control. Few external components are needed: open-LED protection and the Schottky diode are all contained inside the tiny SC70 package. With such a high level of integration, the LT3491 provides a high efficiency LED driver solution in the smallest of spaces.ApplicationsCellular PhonesPDAs, Handheld ComputersDigital CamerasMP3 PlayersGPS Receivers

The LT3492 is a triple output DC/DC converter designed to operate as a constant-current source and is ideal for driving LEDs. The LT3492 works in buck, boost or buck-boost mode. The LT3492 uses a fixed frequency, current mode architecture resulting in stable operation over a wide range of supply and output voltages. A frequency adjust pin allows the user to program switching frequency between 330kHz and 2.1MHz to optimize efficiency and external component size.The external PWM input provides 3000:1 LED dimming on each channel. Each of the three channels has a built-in gate driver to drive an external LED-disconnect P-channel MOSFET, allowing high dimming range. The output current range of each channel of the LT3492 is programmed with an external sense resistor.The CTRL pin is used to adjust the LED current either for analog dimming or over-temperature protection.ApplicationsRGB LightingBillboards and Large DisplaysAutomotive and Avionic LightingConstant-Current Sources

The LT3493 is a current mode PWM step-down DC/DC converter with an internal 1.75A power switch. The wide operating input range of 3.6V to 36V (40V maximum) makes the LT3493 ideal for regulating power from a wide variety of sources, including unregulated wall transformers, 24V industrial supplies and automotive batteries. Its high operating frequency allows the use of tiny, low cost inductors and ceramic capacitors, resulting in low, predictable output ripple.Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge during start-up. The low current (<2µA) shutdown mode provides output disconnect, enabling easy power management in battery-powered systems.VINRangeLT34933.6V to 36V Operating,40V MaximumLT3493-36.8V to 36V Operating,40V MaximumApplicationsAutomotive Battery RegulationIndustrial Control SuppliesWall Transformer RegulationDistributed Supply RegulationBattery-Powered Equipment

The LT3494/LT3494A are low noise boost converters with integrated power switch, Schottky diode and output disconnect circuitry. The parts use a novel* control technique resulting in low output voltage ripple as well as high efficiency over a wide load current range. This technique guarantees that the switching frequency stays above the audio band for the entire load range. The parts feature a high performance NPN power switch with a 350mA and 180mA current limit for the LT3494A and LT3494 respectively. The quiescent current is a low 65µA, which is further reduced to less than 1µA in shutdown. The internal disconnect circuitry allows the output voltage to be isolated from the input during shutdown. An auxiliary reference input (CTRL pin) overrides the internal 1.225V feedback reference with any lower value allowing full control of the output voltage during operation. The LT3494/LT3494A are available in a tiny 8-lead 3mm × 2mm DFN package.ApplicationsOLED PowerLow Noise PowerMP3 Players