DESCRIPTION
The LTC®3731 is a PolyPhase® synchronous step-down switching regulator controller that drives all N-channel external power MOSFET stages in a phase-lockable fixed frequency architecture. The 3-phase controller drives its output stages with 120°phase separation at frequencies of up to 600kHz per phase to minimize the RMS current losses in both the input and output filter capacitors. The 3-phase technique effectively triples the fundamental frequency, improving transient response while operating each control ler at an optimal frequency for efficiency and ease of thermal design. Light load efficiency is optimized by using a choice of output Stage Shedding or Burst Mode operation.

FEATURES
■ 3-Phase Current Mode Controller with Onboard MOSFET Drivers
■ ±5% Output Current Matching Optimizes Thermal Performance and Size of Inductors and MOSFETs
■ Differential Amplifier Accurately Senses VOUT
■ ±1% VREFAccuracy Over Temperature
■ Reduced Power Supply Induced Noise
■ ±10% Power Good Output Indicator
■ 250kHz to 600kHz Per Phase, PLL, Fixed Frequency
■ PWM, Stage SheddingTM or Burst Mode® Operation
■ OPTI-LOOP® Compensation Minimizes COUT
■ Adjustable Soft-Start Current Ramping
■ Short-Circuit Shutdown Timer with Defeat Option
■ Overvoltage Soft Latch
■ Adjustable Undervoltage Lockout Threshold
■ Selectable Phase Output for Up to 12-Phase Operation
■ Available in 5mm ×5mm QFN and 36-Pin Narrow (0.209") SSOP Packages

APPLICATTIOINS
■ Desktop Computers and Servers
■ High Performance Notebook Computers
■ High Output Current DC/DC Power Supplies