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New dc-dc controller eliminates gate charging, switching losses

Posted: 28 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? polyphase? synchronous controller? ltc3731h? dc-dc controller?

Linear Technology Corp. has developed a PolyPhase step-down synchronous controller with guaranteed operation and precision for junction temperatures as high as 140C.

The rugged LTC3731H dc-dc controller has integrated MOSFET drivers and is expandable from 3- to 12-phase operation for 60A to 240A power supply designs. The accuracy of the reference voltage is high, with guaranteed 2 percent accuracy over the entire operating temperature range. Meanwhile, the company said, the precise 5 percent output current matching simplifies thermal management by evenly spreading the heat among the output stages.

Housed in a narrow 36-lead SSOP (5.3mm wide), the new controller product is a single-IC solution for high output distributed power in systems requiring dc-dc conversion from 4.5V to 32V input source to 0.6V to 6V output in buck mode. The LTC3731H configured as 3-phase boost converter delivers high output currents with low output ripple. Competing solutions incorporating MOSFET or inductor sensing introduce as much as 35 percent error in power dissipation between the output stages, resulting in unbalanced power handling and overheating of one or two stages, said Linear Tech. To cope with this excess heat and to prevent thermal stress, designers using competing solutions are forced to over-size the MOSFETs and inductors, adding to the cost and size of the solution.

The LTC3731H incorporates a patented power saving Stage Shedding technique to optimize efficiency and improve battery life at light loads by eliminating the gate charging losses and switching losses of two of its output stages. The PolyPhase operation reduces input ripple current and improves transient response as well as minimizing the requirement for input and output capacitors. The IC operates from 250kHz to 600kHz per phase to achieve an optimal frequency for efficiency, ease of thermal design and use of small inductors and capacitors. And to protect the load and MOSFETs, the LTC3731H is equipped with short-circuit and overload protection as well as soft-start to protect the system from high inrush current.

Target applications for the LTC3731H range from high-end notebook PCs to embedded systems and single-board computers for industrial, instrumentation, telecom and medical systems.

In 1,000-piece orders, pricing starts at $5 each for the LTC3731H.

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