Datasheet LTC3731H (Analog Devices)

LTC3731H 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller FeaTures DescripTion n
3-Phase Current Mode Controller with Onboard
The LTC®3731H 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 LTC3731H is rated for operation n
±2% VREF Accuracy Over Temperature Up to 140°C
up to 140°C junction temperature. The 3-phase controller n Reduced Power Supply Induced Noise drives its output stages with 120° phase separation at n ±10% Power Good Output Indicator frequencies up to 680kHz per phase to minimize the RMS n 225kHz to 680kHz Per Phase, PLL, Fixed Frequency current losses in both the input and output filter capacitors. n PWM, Stage Shedding™ or Burst Mode® Operation The 3-phase technique effectively triples the fundamental n OPTI-LOOP® Compensation Minimizes COUT frequency, improving transient response while operating n Adjustable Soft-Start Current Ramping each controller at an optimal frequency for efficiency and n Short-Circuit Shutdown Timer with Defeat Option ease of thermal design. Light load efficiency is optimized n Overvoltage Soft Latch by using a choice of output Stage Shedding or Burst Mode n Adjustable Undervoltage Lockout Threshold operation. n Selectable Phase Output for Up to 12-Phase The precision reference supports output voltages from Operation 0.6V to 6V. Current foldback provides protection for the n Available in 36-Pin Narrow (0.209") SSOP and external MOSFETs under short-circuit or overload condi- 5mm × 5mm QFN Packages tions. Please refer to the LTC3731 data sheet for 0°C to 70°C and –40°C to 85°C rated versions. applicaTions L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase are registered trademarks and Stage Shedding is a trademark of Linear Technology Corporation. n Automotive and Industrial Power Supplies All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6462525, n High Output Current DC/DC Power Supplies 6304066, 5705919. Typical applicaTion VIN VCC 5V TO 28V VCC TG1 4.5V TO 7V 0.8µH + 0.003Ω LTC3731H 22µF 10µF SW1 35V BOOST1
Efficiency vs I
BG1
OUT
BOOST2 BOOST3 100 0.1µF SENSE1+ 90 VFCB = OPEN SENSE1– SW3 SW2 SW1 V V IN 80 FCB = 5V TG2 V POWER GOOD INDICATOR PGOOD 0.8µH 0.003Ω V FCB = 0V OUT 70 OPTIONAL SYNC IN PLLIN SW2 1.35V 55A 60 PLLFLTR BG2 50 36k PGND VIN UVADJ 40 SENSE2+ 12k EFFICIENCY (%) 680pF SENSE2– 30 VIN ITH TG3 20 0.8µH 0.003Ω 5k RUN/SS V SW3 10 IN = 8V 0.01µF VOUT = 1.5V SGND BG3 0 EAIN 0.1 1 10 100 100pF SENSE3+ LOAD CURRENT (A) 7.5k 3731H F01b SENSE3– + COUT 470µF 6.04k 4V 3731H F01
Figure 1. High Current Triple Phase Step-Down Converter
3731Hfb Document Outline Features Applications 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