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 V output stages with 120 phase separation at frequencies OUT n 1% V Accuracy Over Temperature of up to 600kHz per phase to minimize the RMS current REF n V Range: 0.6V to 5.5V without Diffamp losses in both the input and output filter capacitors. The OUT n 3-phase technique effectively triples the fundamental fre- V Range: 0.6V to (V 1.2V) with Diffamp OUT CC n quency, improving transient response while operating each 250kHz to 600kHz Per Phase, PLL, Fixed Frequency n controller at an optimal frequency for efficiency and ease of PWM, Stage Shedding or Burst Mode Operation n thermal design. Light load efficiency is optimized by using a OPTI-LOOP Compensation Minimizes C OUT n choice of output Stage Shedding or Burst Mode operation. Adjustable Soft-Start Current Ramping 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 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6462525, 630466, n High Performance Notebook Computers 5705919. n High Output Current DC/DC Power Supplies TYPICAL APPLICATION V IN V CC 5V TO 28V V TG1 CC + 4.5V TO 7V 0.8H 0.003 LTC3731 22F 10F SW1 35V BOOST1 BG1 BOOST2 BOOST3 + 0.1F SENSE1 SENSE1 V SW3 SW2 SW1 IN TG2 0.8H POWER GOOD INDICATOR PGOOD 0.003 V OUT SW2 1.35V OPTIONAL SYNC IN PLLIN 55A BG2 PLLFLTR PGND 36k V UVADJ IN + SENSE2 12k 680pF SENSE2 V IN I TH TG3 0.8H 0.003 5k RUN/SS SW3 0.01F SGND BG3 EAIN 100pF + SENSE3 DIFFOUT 7.5k SENSE3 + IN C OUT + IN 470F 6.04k 4V 3731 F01 Figure 1. High Current Triple Phase Step-Down Converter 3731fc 1LTC3731 ABSOLUTE MAXIMUM RATINGS (Note 1) Topside Driver Voltages (BOOSTn) ............. 38V to 0.3V I Voltage ............................................... 2.4V to 0.3V TH Switch Voltage (SWn) ................................... 32V to 5V Operating Ambient Temperature Range Boosted Driver Voltage (BOOSTn SWn) .... 7V to 0.3V LTC3731C ................................................ 0C to 70C Peak Output Current < 1ms (TGn, BGn) ......................5A LTC3731I ..............................................40C to 85C Supply Voltages (V , V ), PGOOD Junction Temperature (Note 2) ............................. 125C CC DR Pin Voltage ................................................... 7V to 0.3V Storage Temperature Range .................. 65C to 125C RUN/SS, PLLFLTR, PLLIN, UVADJ, Lead Temperature G Package (Soldering, 10 sec)..300C FCB Voltages ..............................................V to 0.3V Peak Body Temperature UH Package ................... 240C CC SENSE+, SENSE Voltages ....................... 5.5V to 0.3V PIN CONFIGURATION TOP VIEW 1 36 CLKOUT V CC TOP VIEW 2 35 PGOOD PLLIN 3 34 BOOST1 PLLFLTR 4 33 TG1 FCB 32 31 30 29 28 27 26 25 + 5 32 SW1 IN IN 1 24 BOOST2 6 31 BOOST2 IN DIFFOUT 2 23 TG2 7 30 TG2 DIFFOUT EAIN SW2 3 22 + 8 29 SW2 EAIN SENSE1 4 21 V CC 33 SGND 9 28 V SGND SENSE1 5 20 BG1 DR + + 10 27 BG1 SENSE2 6 19 PGND SENSE1 SENSE2 7 18 BG2 11 26 PGND SENSE1 + SENSE3 8 17 BG3 12 25 BG2 SENSE2 9 10 11 12 13 14 15 16 13 24 BG3 SENSE2 14 23 SW3 SENSE3 + 15 22 TG3 SENSE3 16 21 BOOST3 RUN/SS 17 20 PHASMD I UH PACKAGE TH 32-LEAD (5mm 5mm) PLASTIC QFN 18 19 SGND2 UVADJ T = 125C, = 34C/W JMAX JA EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB G PACKAGE 36-LEAD PLASTIC SSOP T = 125C, = 95C/W, = 32C/W JMAX JA JC 3731fc 2 + + SENSE3 IN RUN/SS FCB I PLLFLTR TH UVADJ PLLIN PHASMD/PG CLKOUT BOOST3 BOOST1 TG3 TG1 SW3 SW1