DC/DC Converter provides step-up and step-down regulation.

Press Release Summary:




Model LT3433 current-mode DC/DC converter operates from input voltage of 4-60 V, delivering regulated outputs between 3.3-20 V and 200 kHz constant frequency operation. Burst Mode® reduces no-load quiescent current to 100 µA. Converter incorporates dual internal 500 mA switches, which seamlessly switch between step-down and step-up voltage conversion. Programmable soft-start helps prevent output overshoot at start-up. Converter comes in 16-lead TSSOP package.



Original Press Release:



60V, IQ=100uA, Step-Up/Step-Down DC/DC Converter



MILPITAS, CA - August 11, 2003 - Linear Technology announces the LT3433, a Burst Mode® operation high voltage (60V), 200kHz, current mode DC/DC converter that provides both step-up and step-down regulation using a single inductor. The LT3433 is the power industry's first high voltage buck-boost regulator. It operates from an input voltage range of 4V to 60V, delivering regulated outputs between 3.3V and 20V.

Certain applications, such as automotive, must regulate a fixed output voltage even though the battery voltage may fluctuate above and below the output. A popular example of this requirement is the "cold-crank" condition encountered in automotive applications. In this instance, a 5V (or 12V) output is required even when the battery voltage declines to 4V during cold crank and quickly returns to a nominal 12-14V immediately following ignition. Although most automotive applications utilize a 12V to 42V nominal input voltage, transient conditions such as "load-dump" or two batteries in series during a jump start require input voltage capability to 60V to reliably operate. The LT3433 offers a 1% regulation transitioning from step-up to step-down in this scenario. Also, as many of these applications are also "always-on," low quiescent current is equally important to preserve battery life when the car is not running. The LT3433's Burst Mode operation reduces no-load quiescent current to only 100uA.

The LT3433 incorporates dual internal 500mA switches, which seamlessly switch between step-down and step-up voltage conversion. Internal control circuitry monitors system conditions and converts from a single switch buck operation to dual switch bridged operation as required by the application. Current limit foldback and frequency foldback help prevent inductor current runaway during start-up, while programmable soft-start helps prevent output overshoot at start-up. Finally, the LT3433's TSSOP-16 package with small externals provides a very compact, thermally enhanced and efficient solution required for space-constrained applications.

The LT3433EFE is available from stock and pricing starts at $3.25 each for 1,000-piece quantities.

Summary of Features: LT3433
Automatic Step-Up/Step-Down Conversion with Single Inductor
Only 100uA Quiescent Current In Burst Mode Operation
4V to 60V Input Voltage Range
2.4V to 20V Output Voltage Range
Dual 500mA Switches
200kHz Constant Frequency Operation
Integrated Soft-Start
16-Lead Thermally Enhanced TSSOP Package

Company Background
Linear Technology Corporation was founded in 1981 as a manufacturer of high performance linear integrated circuits. Linear Technology products include operational, instrumentation and audio amplifiers; voltage regulators,power management devices, DC-DC converters and voltage references; comparators; monolithic filters; communications interface circuits; one-chip data acquisition sub-systems; pulse-width modulators and sample-and-hold devices; and high frequencydevices. Applications for Linear Technology's high performance circuits include wireless and broadband telecommunications infrastructure, cellular telephones, networking products and satellite systems, notebook and desk top computers, computer peripherals, video/multimedia, industrial and medical instrumentation, automotive electronics, factory automation, process control, military and space systems, and high-end consumer products including digital cameras, MP3 players and other electronic products.

READER SERVICE: Call toll-free 1-800-4-LINEAR (for literature only), or go to the company's web site: www.linear.com

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