DC/DC controller keeps quiet at high currents

Up to 12 phases can be paralleled and clocked out-of-phase to minimise input and output filtering requirements in high-current applications (up to 200A).

The LTC3811 from Linear Technology is a dual-output synchronous step-down DC/DC controller with multiphase operation, differential output voltage sensing and integrated phase-lock loop (PLL) synchronisation.

Up to 12 phases can be paralleled and clocked out-of-phase to minimise input and output filtering requirements in 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 LTC3811 operates with all N-channel MOSFETs from input voltages ranging from 4.5 to 30V and is optimised for low output voltages from 0.6 to 3.3V.

The onboard 0.9ohm powerful gate drivers minimise MOSFET switching losses and allow the use of multiple MOSFETs connected in parallel for very high current applications.

The operating frequency can be programmed from 250 to 750kHz or can be synchronised to an external clock with internal PLL from 150 to 900kHz.

The LTC3811 uses peak current mode control with a minimum on-time of 65ns and responds almost instantly to a transient event.

In addition, the LTC3811 current limit sense threshold can be programmed from 24 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 reference voltage accuracy is a best in class +/-0.5% over an operating temperature range of -40 to +85C.

Tracking and sequencing functions enable optimisation of power-up and power-down of multiple power supplies.

Additional features include an onboard 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 5 x 7mm QFN package.

The 1000-piece price starts at US $3.75 each.

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