550kHz, PolyPhase, High Efficiency, Synchronous Step-Down Switching Regulator

The LTC3729 is a multiple phase, synchronous step-down current mode switching regulator controller that drives N-channel external power MOSFET stages in a phase-lockable fixed frequency architecture. The PolyPhase controller drives its two output stages out of phase at frequencies up to 550kHz to minimize the RMS ripple currents in both input and output capacitors. The output clock signal allows expansion for up to 12 evenly phased controllers for systems requiring 15A to 200A of output current. The multiple phase technique effectively multiplies the fundamental frequency by the number of channels used, improving transient response while operating each channel at an optimum frequency for efficiency. Thermal design is also simplified.

An internal differential amplifier provides true remote sensing of the regulated supply’s positive and negative output terminals as required for high current applications.

A RUN/SS pin provides both soft-start and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipation during short-circuit conditions when the overcurrent latchoff is disabled. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3729 includes a power good output pin that indicates when the output is within ±7.5% of the designed set point.

Vin Max

Vref

LTC3729

36V

0.8

LTC3729L-6

30V

0.6

Applications

* Desktop Computers

* Large Memory Arrays

* DC Power Distribution Systems

* Wide VIN Range: 4V to 36V Operation

* Reduces Required Input Capacitance and Power Supply Induced Noise

* ±1% Output Voltage Accuracy

* Phase-Lockable Fixed Frequency: 250kHz to 550kHz

* True Remote Sensing Differential Amplifier

* PolyPhase™ Extends from Two to Twelve Phases

* Reduces the Size and Value of Inductors

* Current Mode Control Ensures Current Sharing