Chipset enables flexible power supply design

National Semiconductor has developed an integrated high-voltage cascaded DC/DC controller ideal for power conversion in computer and communications systems.

National Semiconductor has developed an integrated high-voltage cascaded DC/DC controller ideal for power conversion in computer and communications systems.

National has also released two 100V power mosfet drivers that work seamlessly with the new controller, providing customers with a chipset solution for communications power systems, automotive power systems, -48V distributed power systems, motor drive systems, industrial power supplies and half-bridge and full-bridge convertors.

"The cascaded controller-driver chipset puts National Semiconductor in the forefront of the high-voltage power IC market", said Johan Hedman, Product Marketing Manager for National Semiconductor's Power Management Group in Europe.

"Offering customers a unique combination of strong design capability, manufacturing strength and innovative packaging, National is the only company that provides such a high level of integration in the smallest package".

The evaluation board for the chipset will be on display at the Applied Power Electronics Conference and Exposition (APEC) 2003, from 9th to 13th February at the Fontainebleau Hotel in Miami Beach, FL.

The chipset is endorsed by industry leaders such as Magnetek, a major digital power supply manufacturer.

"Magnetek chose National Semiconductor because of their innovative solution", said Lorenzo Cincinelli, CTO at Magnetek in Italy.

"The high integration level of National's high-voltage devices will allow us to produce telecomms power supply modules with outstanding performances and reliability levels".

The cascaded buck-fed topology is preferred in applications with a large voltage step-down ratios, the turns ratio of the isolation transformer allows the buck preregulator to operate at larger duty cycles, improving efficiency.

National's LM5041-LM5102 chipset simplifies control, drive and regulation in cascaded buck-fed topologies.

The LM5102 100V synchronous buck driver drives the step-down convertor control and synchronous mosfets into the current source inductor or inductor-capacitor filter; this feeds the primary centre tap of a push-pull convertor isolation transformer.

The LM5041 drives the push-pull mosfets directly and the buck preregulator indirectly through the LM5102 with a PWM signal from its current-mode controller.

National's new LM5041 is an integrated current-mode pulsewidth-modulated (PWM) controller incorporating a buck preregulator controller synchronised to push-pull mosfet drivers with peak currents of 2A and programmable dead time.

A high-speed controller with a user-programmable 1MHz oscillator, external clock synchronisation capability and current limit propagation delay of less than 100ns, the LM5041 integrates onto a single die, unique features such as: fully integrated synchronous buck control and push-pull drivers with programmable dead time; a wide range, 15-100V start-up bias regulator; high-speed, 2A peak push-pull mosfet drivers; user-programmable soft-start circuitry; and a tiny, thermally enhanced, 16-pin leadless lead frame package (LLP-16, 5 x 5mm).

The LM5101 and LM5102 are 100V half-bridge power mosfet drivers designed to drive both the high side and low side N-channel mosfets in a synchronous buck or a half-bridge configuration.

The LM5101/LM5102 and the LM5041 form a complete chipset solution, providing customers with flexibility to scale power mosfets to the power requirements of the DC/DC convertor.

A second LM5101 can be applied at the push-pull outputs of the LM5041 for customers preferring cascaded half or full-bridge topologies.

The LM5102 also provides programmable rise-time control that allows designers to "tune" the power supply for maximum efficiency and limit EMI.

The LM5101 and LM5102 feature: a 100V synchronous-buck driver which mates with the LM5041 100 V cascaded controller; user-programmable turn-on edge delay feature (on the LM5102 driver); and a tiny, thermally enhanced 10-pin leadless lead frame package (LLP-10, 4 x 4mm).

National Semiconductor's LM5041 cascaded controller in a LLP-16 package is priced at $2.55 each in 1000 quantities.

The LM5101 and LM5102, both in a LLP-10 package, are priced at $1.75 each and $1.79 each in 1000 quantities, respectively.

The LM5041 and LM5100s will be available for sampling in April with volume production in June and September, respectively.

(This was Electronicstalk's Top Story on 6 February 2003).

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