New Industry Products

National Semi Offers 65V Dual-Channel, Dual-Phase Synchronous Buck Controller for High Voltage Applications

September 19, 2010 by Jeff Shepard

National Semiconductor Corp. introduced the LM5119, a high voltage, dual-channel, dual-phase, synchronous buck controller with emulated current-mode (ECM) control. The LM5119 enables regulation of single or dual high-current voltages directly from inputs as high as 65V, simplifying high voltage dc-dc conversion and reducing PCB footprint by up to 50% versus alternative solutions requiring two conversion stages. The LM5119 features what the company says is a unique combination of high performance, flexibility and ease-of-use for demanding telecommunication, automotive and industrial control applications that require accurate voltage regulation. The device expands National’s portfolio of high voltage synchronous buck controllers to address higher load currents.

Today’s telecommunication, automotive and industrial control applications must regulate low output voltages at increasing load currents from a high input voltage that can change widely while still meeting stringent PCB space and efficiency requirements. According to the National Semi, traditional approaches require two dc-dc conversion stages: one to regulate an intermediate bus voltage of approximately 9 to 12V and a second to regulate the specific load voltages that can be as low as 1V and can require currents in excess of 20A. National’s LM5119 enables direct regulation of two output voltages from an input, eliminating the need for an intermediate bus conversion stage that limits efficiency and requires up to twice the number of components. National’s proprietary ECM control technology enables precise control of very small duty cycles necessary in high voltage applications, which allows accurate regulation of DC output voltages with excellent transient response. For high-current output requirements, the two outputs can be connected in parallel to power loads up to 40A with interleaved switching that minimizes input and output capacitance.

National’s LM5119 features a wide operating voltage range of 5.5 to 65V and a 0.8V, 1.5% reference enables accurate regulation of load voltages from 0.8V up to 90% of the input voltage. The operating frequency is user-programmable from 50 kHz up to 750 kHz and can be synchronized to an external clock signal. Diode emulation mode (DEM) enables discontinuous inductor current operation at light load conditions for improved efficiency. This mode allows controlled start-up into a pre-biased load by preventing current flow into the synchronous MOSFET. A high voltage bias regulator with automatic switch-over to external bias further improves efficiency. Additional features include thermal shutdown, cycle-by-cycle and hiccup mode current limit and adjustable line under-voltage lockout. The wide Vin range, multi-phase operation, programmable soft-start, input UVLO and diode emulation mode together enhance the system designer’s flexibility and control of all applications.

The LM5119 is offered in a 5 x 5mm 32-pin LLP package, and is priced at $4.05 and the LM25119 is $3.80 in 1,000-unit quantities.