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Multiphase DC/DC controller suits power audio amps

Posted: 14 Sep 2007 ?? ?Print Version ?Bookmark and Share

Keywords:DC/DC controller? output voltage sensing? audio amplifier?

Linear Technology Corp. has unveiled the LTC3811 dual output synchronous step-down DC/DC controller with multiphase operation, differential output voltage sensing and integrated PLL synchronization.

The LTC3811 can have up to 12 phases paralleled and clocked out-of-phase to minimize the input and output filtering requirements for high current applications (up to 200A). The differential amplifier provides true remote output voltage sensing, enabling high accuracy regulation where IR losses occur through vias, trace runs and interconnects. Applications include high current ASIC supplies, power distribution buses, high power audio amplifiers and network servers.

The DC/DC controller operates with all N-channel MOSFETs from input voltages ranging from 4.5V to 30V and is optimized for low output voltages from 0.6V to 3.3V. The on-board 0.9? gate drivers minimize MOSFET switching losses and allow the use of multiple MOSFETs connected in parallel for very high current applications.

In addition, LTC3811's operating frequency can be programmed from 250- to 750kHz or can be synchronized to an external clock with internal PLL from 150kHz to 900kHz. The LTC3811 uses peak current mode control with a minimum on-time of 65nS and responds almost instantly to a transient event. The LTC3811 current limit sense threshold can be programmed from 24mV to 85mV, allowing the use of DCR sensing of the output inductors voltage drop or with a discrete sense resistor. In either case, the current limit is user-programmable, ensuring optimum system efficiency and excellent control over the maximum output current.

The LTC3811 VREF accuracy is 0.5 percent over an operating temperature range of -40C to 85C. Also, tracking and sequencing functions enable optimization of power-up and power-down of multiple power supplies. Additional features include an on-board LDO for IC power and gate drive, programmable soft start, two power good signals and external VCC control for the optional use of an external voltage to power the chip.

The LTC3811 is offered in a 36-lead SSOP or a 38-lead 5mm x 7mm QFN package. The 1,000-piece price starts at $3.75 each.




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