Analog Devices

The LT3473/LT3473A are micropower step-up DC/DC converters with integrated Schottky diode and output disconnect circuitry in low profile DFN packages. The small package size, high level of integration and the use of tiny SMT components yield a solution size of less than 50mm2. The internal 1A switch allows the device to deliver 25V at up to 80mA from a Li-Ion cell, while automatic Burst Mode operation maintains efficiency at light load. An auxiliary reference input (CTRL) allows the user to override the internal 1.25V feedback reference with any lower value, allowing full control of the output voltage during operation. APGOODpin sinks current when the output voltage reaches 90% of final value.The LT3473A includes two NPN transistors for generating intermediate bias voltages from the output and is offered in a 12-lead (4mm × 3mm) DFN package. The LT3473 does not include these NPNs and is offered in an 8-lead (3mm × 3mm) package.The rugged 36V switch and output disconnect circuitry allow outputs up to 34V to be easily generated in a simple boost topology.ApplicationsOLED BiasCCD Bias

The LT3474/LT3474-1 are fixed frequency step-down DC/DC converters designed to operate as constant-current sources. An internal sense resistor monitors the output current allowing accurate current regulation, ideal for driving high current LEDs. High output current accuracy is maintained over a wide current range, from 35mA to 1A, allowing a wide dimming range.Unique PWM circuitry allows a dimming range of 400:1, avoiding the color shift normally associated with LED current dimming.The high switching frequency offers several advantages, permitting the use of small inductors and ceramic capacitors. Small inductors combined with the 16 lead TSSOP surface mount package save space and cost versus alternative solutions. The constant switching frequency combined with low-impedance ceramic capacitors result in low, predictable output ripple.With their wide input range of 4V to 36V, the LT3474/ LT3474-1 regulate a broad array of power sources, from 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. A current mode PWM architecture provides fast transient response and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.ApplicationsAutomotive and Avionic LightingArchitectural Detail LightingDisplay BacklightingConstant Current Sources

The LT3475 is a dual step-down DC/DC converter designed to operate as a constant-current source. An internal sense resistor monitors the output current allowing accurate current regulation ideal for driving high current LEDs. The high side current sense allows grounded cathode LED operation. High output current accuracy is maintained over a wide current range, from 50mA to 1.5A, allowing a wide dimming range. Unique PWM circuitry allows a dimming range of 3000:1, avoiding the color shift normally associated with LED current dimming.The high switching frequency offers several advantages, permitting the use of small inductors and ceramic capacitors. Small inductors combined with the LT3475's 20 lead TSSOP surface mount package save space and cost versus alternative solutions. The constant switching frequency combined with low-impedance ceramic capacitors result in low, predictable output ripple.With its wide input range of 4V to 36V, the LT3475 regulates a broad array of power sources. A current mode PWM architecture provides fast transient response and cycle-by-cycle current limiting. Frequency foldback and thermal shutdown provide additional protection.ApplicationsAutomotive and Avionic LightingArchitectural Detail LightingDisplay BacklightingConstant-Current Sources

The LT3476 is a quad output DC/DC converter designed to operate as a constant-current source for driving high current LEDs. A fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A frequency adjust pin allows the user to program switching frequency between 200kHz and 2MHz to optimize efficiency and external component size.The LT3476 senses output current at the high side of the LED. High side current sensing is the most flexible scheme for driving LEDs, allowing buck, boost or buckboost configurations. Each current monitor threshold is trimmed to within 2.5% at the full scale of 105mV. With an external sense resistor, the user programs the output current range of each channel. Each of the four regulators is independently operated by that channel’s PWM signal. This PWM feature allows precise adjustment of the color mixing or dimming ratio of the LED source. Dimming ratios up to 1000:1 can be achieved.ApplicationsRGGB LightingAutomotive and Avionic LightingTFT LCD BacklightingConstant-Current Sources

The LT3477 is a current mode, 3A DC/DC step-up converter with dual rail-to-rail current sense amplifiers and an internal 3A, 42V switch. It combines a traditional voltage feedback loop and two unique current feedback loops to operate as a constant-current, constant-voltage source. Both current sense voltages are set at 100mV and can be adjusted independently using the IADJ1and IADJ2pins. Efficiency of up to 93% can be achieved in typical applications. The LT3477 features a programmable soft-start function to limit inductor current during start-up. Both inputs of the error amplifier are available externally allowing positive and negative output voltages (boost, inverting, SEPIC, Flyback). The switching frequency is programmable from 200kHz to 3.5MHz through an external resistor.Available in thermally enhanced 20-pin (4mm × 4mm) QFN and 20-pin TSSOP packages, the LT3477 provides a complete solution for both constant-voltage and constantcurrent applications.ApplicationsHigh Power LED DriverDSL ModemsDistributed PowerInput/Output Current Limited Boost, SEPIC, Inverting, Flyback ConvertersConstant-Voltage, Constant-Current Source

The LT3479 is a current mode, fixed frequency step-up DC/DC converter with an internal 3A, 42V switch. Efficiencies of up to 89% can be achieved in typical applications. It features a programmable soft-start function to limit inductor current during start-up and inrush current protection to protect the LT3479 during shorts and line transients. Both inputs of the error amplifier are available to the user allowing positive and negative output voltages. Through an external resistor, the user can program the switching frequency from 200kHz to 3.5MHz. The low profile (0.75mm) 14-pin, 4mm × 3mm DFN package provides excellent thermal performance in a small footprint. The LT3479 is also available in a thermally enhanced 16-pin TSSOP package.ApplicationsHigh Power LED DriverDSL ModemsDistributed Power

The LT3480 is an adjustable frequency (200kHz to 2.4MHz) monolithic buck switching regulator that accepts input voltages up to 36V (60V maximum). A high efficiency 0.25Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control, and logic circuitry. Current mode topology is used for fast transient response and good loop stability. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3480 can further enhance low output current efficiency by drawing bias current from the output when VOUTis above 3V. Shutdown reduces input supply current to less than 1µA while a resistor and capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good flag signals when VOUTreaches 86% of the programmed output voltage. The LT3480 is available in 10-Pin MSOP and 3mm × 3mm DFN packages with exposed pads for low thermal resistance.ApplicationsAutomotive Battery RegulationPower for Portable ProductsDistributed Supply RegulationIndustrial Supplies

The LT3482 is a fixed frequency current mode step-up DC/DC converter with voltage doubler designed to bias avalanche photodiodes (APDs) in optical receivers. It can provide up to 90V output. The LT3482 features high side APD bias current monitoring with better than 10% relative accuracy over the entire temperature range. The integrated power switch, Schottky diodes and APD bias current monitor allow a small converter footprint and low solution cost. Constant switching frequency results in predictable output noise that is easy to filter. The inductor-based topology ensures an input free from switching noise. An integrated high side current monitor produces a current proportional to APD bias current with better than 10% relative accuracy over four decades of dynamic range in the input range of 250nA to 2.5mA. This APD bias current can be used as a reference to provide a digitally programmed output voltage via the CTRL pin. The LT3482 is available in the tiny footprint (3mm × 3mm) 16-lead QFN package.ApplicationsAPD BiasPIN Diode BiasOptical Receivers and ModulesFiber Optic Network Equipment