Power Electronics

Stepdown Controller Supports 3-Phase Switching

Linear Technology’s LTC3773 is a triple output, 3-phase current mode synchronous stepdown switching regulator controller with output voltage tracking. This controller provides a power management solution for FPGA, DSP and other multi-supply applications.

The device features fixed frequency operation from 200 kHz to 600 kHz, synchronizable up to 750 kHz. The reference has an accuracy of 1%.

The LTC3773 is composed of three independent synchronous buck regulator controllers. On-chip high-side and low-side synchronous rectifier drivers are integrated to drive n-channel MOSFETs from input voltages of 4 V to 36 V. The input ripple current is minimized by operating each controller 120° out of phase, allowing a smaller input capacitor and inductor resulting in reduced power supply cost. The LTC3773 automatically adjusts from PWM mode to Burst Mode operation to maintain high efficiency under light-load conditions. In addition, two or all of the three outputs can be paralleled for higher current requirements.

This controller meets all the FPGA and DSP startup profile requirements, including monotonic voltage ramp and minimum voltage-rail rise time. Furthermore, the LTC3773 allows for coincident or ratiometric tracking. Independent enables for each output allow sequencing to minimize demand on the power supply at start-up. Soft start on each supply limits inrush current during startup. All three supply voltages are offered in user-programmable options for maximum flexibility.

The LTC3773 is offered in a 36-Lead SSOP or a 38-Lead 5-mm x 7-mm QFN package. The 1000-piece price starts at $3.95.

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