Multiphase Step-Down DC/DC Controller with Differential Output Voltage Sensing & PLL

The LTC3811 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 ohm powerful gate drivers minimize 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 250kHz to 750kHz or can be synchronized to an external clock with internal phase-lock-loop (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. In addition, 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 a best in class ±0.5% over an operating temperature range of -40°C to 85°C. 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.