Flyback Controller operates at 250 kHz constant frequency.

Press Release Summary:




Model LTC3806 synchronously drives primary and secondary side MOSFETs. It facilitates cross regulation in multiple output power supplies by keeping MOSFETs ON and outputs coupled for larger fraction of each power conversion cycle. Unit incorporates all timing and control functions, as well as 1 A gate drivers for designing multiple output power supply at up to 60 W. Adjustable soft-start controls inrush current while IC's start-up current is guaranteed at 80 µA.



Original Press Release:



Synchronous Flyback Controller Improves Efficiency & Cross Regulation in Multiple Output, Non-Isolated Supplies



MILPITAS, CA - January 29, 2004 - Linear Technology Corporation introduces the LTC3806, a flyback controller that synchronously drives both primary and secondary side MOSFETs to improve efficiency and cross regulation. Compared to a non-synchronous design, the LTC3806 eliminates the use of diodes that reduce power supply efficiency and generate heat. Moreover, existing synchronous flyback solutions must use external MOSFET driver ICs and require either an additional pulse transformer or a careful timing delay circuitry to protect the MOSFETs against simultaneous conduction. The IC improves cross regulation in multiple output power supplies by keeping the MOSFETs ON and the outputs coupled for a larger fraction of each power conversion cycle. The LTC3806 incorporates all the timing and control functions, as well as 1A gate drivers for designing a multiple output power supply at up to 60W that operates with 89% efficiency. The LTC3806 is a simple and efficient controller for converting a high voltage input supply such as 48V, 42V, or 12V to multiple low voltage outputs such as 12V, 5V, 3.3V and 2.5V. Applications include telecom, automotive, industrial, test and medical power systems that require multiple low voltage rails.

The LTC3806 is a current mode flyback converter with excellent transient response. To minimize voltage transients and avoid system reset at start-up, an adjustable soft-start controls inrush current while the IC's start-up current is guaranteed at only 80uA. The on-board 1.23V reference is accurate to ±1%. The LTC3806 operates at nominal 250kHz constant frequency for ease of noise filtering and small transformer design.

The LTC3806 is rated for operation from -40°C to 85°C and is housed in a 3mm x 4mm DFN package. 1,000-piece pricing starts at $3.40 each.

Summary of Features: LTC3806
Synchronous Flyback for High Operating Efficiency
Better Cross Regulation Than Non-Synchronous Converters
Soft-Start Minimized Inrush Current
Current Mode Control for Excellent Transient Response
Constant Frequency Operation (Never Audible)
Small 3mm x 4mm 12-Pin DFN 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.

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