Datasheet LTC3731 (Analog Devices)

LTC3731 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller
FEATURES DESCRIPTION
n
3-Phase Current Mode Controller with Onboard
The LTC®3731 is a PolyPhase® synchronous step-down
MOSFET Drivers
switching regulator controller that drives all N-channel n
±5% Output Current Matching Optimizes Thermal
external power MOSFET stages in a phase-lockable fixed
Performance and Size of Inductors and MOSFETs
frequency architecture. The 3-phase controller drives its n
Differential Amplifier Accurately Senses VOUT
output stages with 120° phase separation at frequencies n ±1% VREF Accuracy Over Temperature of up to 600kHz per phase to minimize the RMS current n VOUT Range: 0.6V to 5.5V without Diffamp losses in both the input and output filter capacitors. The n V 3-phase technique effectively triples the fundamental fre- OUT Range: 0.6V to (VCC – 1.2V) with Diffamp n 250kHz to 600kHz Per Phase, PLL, Fixed Frequency quency, improving transient response while operating each n PWM, Stage Shedding™ or Burst Mode® Operation controller at an optimal frequency for efficiency and ease of n OPTI-LOOP® Compensation Minimizes C thermal design. Light load efficiency is optimized by using a OUT n Adjustable Soft-Start Current Ramping choice of output Stage Shedding or Burst Mode operation. n Short-Circuit Shutdown Timer with Defeat Option A differential amplifier provides true remote sensing of n Overvoltage Soft Latch both the high and low side of the output voltage at the n Adjustable Undervoltage Lockout Threshold point of load. n Selectable Phase Output for Up to 12-Phase Operation Soft-start and a defeatable, timed short-circuit shutdown n Available in 5mm × 5mm QFN and 36-Pin Narrow protect the MOSFETs and the load. Current foldback (0.209") SSOP Packages provides protection for the external MOSFETs under short-circuit or overload conditions.
APPLICATIONS
L, LT, LTC, LTM, Bust Mode, OPTI-LOOP, PolyPhase, Linear Technology and the Linear logo are registered and Stage Shedding is a trademark of Linear Technology Corporation. All other n Desktop Computers and Servers trademarks are the property of their respective owners. Protected by U.S. Patents, including n High Performance Notebook Computers 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6462525, 630466, 5705919. n High Output Current DC/DC Power Supplies
TYPICAL APPLICATION
VIN VCC 5V TO 28V VCC TG1 4.5V TO 7V 0.8µH + 0.003Ω LTC3731 22µF 10µF SW1 35V BOOST1 BG1 BOOST2 BOOST3 0.1µF SENSE1+ SENSE1– SW3 SW2 SW1 VIN TG2 POWER GOOD INDICATOR PGOOD 0.8µH 0.003Ω VOUT OPTIONAL SYNC IN PLLIN SW2 1.35V 55A PLLFLTR BG2 36k PGND VIN UVADJ SENSE2+ 12k 680pF SENSE2– VIN ITH TG3 0.8µH 0.003Ω 5k RUN/SS SW3 0.01µF SGND BG3 EAIN 100pF DIFFOUT SENSE3+ 7.5k SENSE3– IN– + COUT IN+ 470µF 6.04k 4V 3731 F01
Figure 1. High Current Triple Phase Step-Down Converter
3731fc 1 Document Outline Features Applications Features Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Functional Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts