Linear LTC3855 synchronous step-down DC/DC controller

Linear has introduced the LTC3855, a dual-output high-efficiency (up to 95%) 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 for high current applications (up to 200 A).

The differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling high accuracy regulation where IR losses occur through vias, trace runs and interconnects.

Applications include high-current ASIC and FPGA supplies, power distribution buses, high-power audio amplifiers and network servers.

The device operates with all N-channel MOSFETs from input voltages ranging from 4.5 to 38 and it can produce ±0.75% accurate output voltages from 0.6 to 12.5.

Output current is sensed by monitoring the voltage drop across the output inductor or by using a sense resistor. Programmable DCR temperature compensation maintains an accurate and constant overcurrent limit over a broad temperature range.

The onboard 1.1 Ω gate driver minimises MOSFET switching losses and allows the use of multiple MOSFETs connected in parallel. A fixed operating frequency can be programmed from 250 to 770 kHz or can be synchronised to an external clock with its internal PLL. The device’s minimum on-time of 90 ns makes it suitable for high step-down ratio applications.