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National Semiconductor introduces 75 V, 2.5 A integrated buck regulator

National Semiconductor Corporation has introduced a high-frequency buck regulator that steps down an input voltage from 7 V to 75 V to produce a regulated 2.5 A power supply, adjustable from 1.225 V to 65 V. The LM5005 is optimized for 48 V automotive and other power supply applications.

Paul Greenland, director of strategic marketing for National's Power Management Group, said the LM5005 complements the firm's 75 V, 1.0 A LM5010 and 75 V, 0.5 A LM5007 buck regulators. The LM5005 integrates a 75 V N-channel MOSFET and employs and proprietary scheme that uses emulated current-mode pulse-width modulation to produce a 2.5 A step-down regulator with miminal external components.

Greenland said the proprietary control method generates an internal emulated inductor current ramp that significantly reduces the noise sensitivity of the controller, thus allowing the LM5005 to control very small duty cycles reliably so that designers can take advantage of the part's 75 V input range and 500 kHz frequency capabilities. He added that current-mode control provides line voltage feed-forward and simplified loop compensation.

Operating frequency is programmable from 50 kHz to 500 kHz. A bidirectional oscillator synchronization pin allows multiple LM5005 regulators to self-synchronize or switch synchronously with an external clock. Additional protection features include current limit, thermal shutdown and remote shutdown capability. The device is available in the TSSOP-20 package, with an exposed mounting pad for beter thermal dissipation.

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