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Linear Tech buck controller provides current balancing

Posted: 26 Jul 2002 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? ltc3732? polyphase buck controller? voltage regulator ic? power supply regulator ic?

Using a current-mode architecture, the LTC3732 three-phase buck controller from Linear Technology Corp. provides output currents of up to 60A while maintaining current balancing between the three output power stages to within 15 percentlower than the 30 percent found in other designs.

This allows a given power supply to have precision current sharing between the output stages for improved thermal performance and reliability.

The polyphase device drives an n-channel external MOSFET in a phase-locked fixed frequency architecture. It also drives its output stages with 120: phase separation at frequencies of up to 600kHz per phase to minimize the rms current dissipated by the ESR of the I/O filter capacitors.

To optimize efficiencies at light loads, the LTC3732 switches between output stage shedding and Burst Mode operation. The regulator also has an integrated 5-bit VID DAC that enables output voltages from 1.075V to 1.85V to be programmed in 25mV increments to conform to Intel's VRM 9.0 and 9.1 requirements.

A differential amplifier provides remote sensing of both the high and low side of the output voltage at load points, enabling 11 percent output voltage accuracy. A Soft-start and a timed short-circuit shutdown protects the MOSFETs and the load, while a foldback current limit circuit provides protection during short-circuit or overload conditions.

The LTC3732 is housed in a 36-pin SSOP casing and is characterized over the commercial temperature range of 0:C to 70:C. Pricing starts at $4.35 each in 1,000-piece quantities.

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