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PWM controllers provide flexibility

Posted: 11 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:national semiconductor? national semi? pulse-width modulation controller? pwm controller? lm5032?

National Semiconductor Corp. rolled out what it bills as the industry's first 100V dual interleaved pulse-width modulation (PWM) controllers for conventional single-ended and active-clamp reset topologies.

Giving power supply designers flexibility, the LM5032 and LM5034 controllers can be configured to control either two independently regulated outputs or a single, high-current output from two primary power stages. In the first case, the two PWM channels operate 180 out of phase with one another, or are interleaved, which reduces the input ripple current. Meanwhile, in the single-output configuration, the interleaving also reduces ripple current in the output filter capacitor.

"Interleaved power conversion is increasingly useful, especially in dense, high-power applications that require significant filter capacitance to manage high-input peak switching or ripple current," commented Paul Greenland, director of product marketing for National's Power Management group.

The LM5032 and LM5034 are the company's first products designed for interleaved isolated single-ended dc-dc converters. These two controllers feature a propagation delay of less than 100nS and a 2MHz-capable, single-resistor-adjustable oscillator that can be synchronized externally. Both chips integrate two of National's compound, bipolar-CMOS, 2.5A MOSFET gate drivers, and also feature user-adjustable maximum duty cycle, hiccup-mode fault protection with adjustable restart delay, adjustable input under-voltage sensing, and a direct optocoupler interface.

The LM5034 provides two additional gate drivers for P-channel active-clamp MOSFETs with user-programmable dead-time control. National added that the product' active-clamp transformer reset achieves superior conversion efficiency compared with conventional single-ended power supply topologies. Other features include a high-voltage start-up regulator that operates over a wide input range of 12V to 100V, as well as cycle-by-cycle current limit, slope compensation and over-temperature protection.

The LM5032 controller can be used for designing dual-interleaved boost, flyback or standard forward converters, while the LM5034 is specifically designed for interleaved forward converters with active clamp transformer reset.

The LM5032, in a TSSOP-16 package, is priced at $1.55 each, and the LM5034, in a TSSOP-20 package, is available for $1.90 each, both in 1,000-unit quantities.

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