LTC3728 Dual, 550kHz, 2-Phase Synchronous Step-Down Switching Regulator FEATURES DESCRIPTION n Dual, 180 Phased Controllers Reduce Required The LTC 3728 is a dual high performance step-down Input Capacitance and Power Supply Induced Noise switching regulator controller that drives all N-channel n OPTI-LOOP Compensation Minimizes C synchronous power MOSFET stages. A constant-frequency OUT n 1% Output Voltage Accuracy current mode architecture allows phase-lockable frequency n Power Good Output Voltage Indicator of up to 550kHz. Power loss and noise due to the ESR of n Phase-Lockable Fixed Frequency 250kHz to 550kHz the input capacitors are minimized by operating the two n Dual N-Channel MOSFET Synchronous Drive controller output stages out of phase. n Wide V Range: 3.5V to 36V Operation IN OPTI-LOOP compensation allows the transient response to n Very Low Dropout Operation: 99% Duty Cycle be optimized over a wide range of output capacitance and n Adjustable Soft-Start Current Ramping ESR values. The precision 0.8V reference and power good n Foldback Output Current Limiting output indicator are compatible with future microprocessor n Latched Short-Circuit Shutdown with Defeat Option generations, and a wide 3.5V to 30V (36V maximum) input n Output Overvoltage Protection supply range encompasses all battery chemistries. n Remote Output Voltage Sense n A RUN/SS pin for each controller provides both soft- Low Shutdown I : 20A Q n 5V and 3.3V Regulators start and optional timed, short-circuit shutdown. Current n foldback limits MOSFET dissipation during short-circuit 3 Selectable Operating Modes: Constant-Frequency, conditions when overcurrent latchoff is disabled. Output Burst Mode Operation and PWM n overvoltage protection circuitry latches on the bottom Available in 32-Pin 5mm 5mm QFN and 28-Pin SSOP Packages MOSFET until V returns to normal. The FCB mode OUT pin can select among Burst Mode, constant-frequency APPLICATIONS mode and continuous inductor current mode or regulate n Notebook and Palmtop Computers a secondary winding. The LTC3728 includes a power good n Telecom Systems output pin that indicates when both outputs are within n Portable Instruments 7.5% of their designed set point. n Battery-Operated Digital Devices L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other trademarks are the property n DC Power Distribution Systems of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 5705919. V TYPICAL APPLICATION IN + C 5.2V TO 28V IN 4.7F 1F 22F D3 V PGOOD INTV D4 IN CC M1 M2 50V TG1 TG2 L1 L2 BOOST1 BOOST2 3.2H 3.2H C , 0.1F C , 0.1F B2 B1 SW1 SW2 LTC3728 BG1 BG2 f IN PLLIN PGND 500kHz + + SENSE1 SENSE2 R R SENSE2 SENSE1 1000pF 1000pF 0.01 0.01 SENSE1 SENSE2 V V V V OUT2 OUT1 OSENSE1 OSENSE2 R2 R4 3.3V 5V I I TH1 TH2 105k 63.4k C C C C 5A OUT1 C1 C2 OUT 5A RUN/SS1 SGND RUN/SS2 + R1 R3 47F 1% 220pF 220pF 1% 56F 20k R C C 20k 6V 6V C1 SS1 SS2 R C2 1% 15k 1% SP 0.1F 0.1F SP 15k M1, M2: FDS6982S 3728 F01 Figure 1. High Ef ciency Dual 5V/3.3V Step-Down Converter 3728fg 1 +LTC3728 ABSOLUTE MAXIMUM RATINGS (Note 1) I I , V , V Voltages ... 2.7V to 0.3V Input Supply Voltage (V ) .........................36V to 0.3V TH1, TH2 OSENSE1 OSENSE2 IN Peak Output Current <10s (TG1, TG2, BG1, BG2) .....3A Topside Driver Voltages INTV Peak Output Current ................................. 50mA (BOOST1, BOOST2) ............................... 42V to 0.3V CC Operating Temperature Range (Note 7).... 40C to 85C Switch Voltage (SW1, SW2) ......................... 36V to 5V Junction Temperature (Note 2) ............................. 125C INTV EXTV , RUN/SS1, RUN/SS2, CC, CC Storage Temperature Range ................... 65C to 125C (BOOST1-SW1), (BOOST2-SW2), PGOOD ..... 7V to 0.3V + + Lead Temperature (Soldering, 10 sec) SENSE1 , SENSE2 , SENSE1 , (G Package Only) .................................................. 300C SENSE2 Voltages .........................(1.1)INTV to 0.3V CC PLLIN, PLLFLTR, FCB Voltages ............ INTV to 0.3V CC PIN CONFIGURATION TOP VIEW TOP VIEW RUN/SS1 1 28 PGOOD + 2 TG1 SENSE1 27 32 31 30 29 28 27 26 25 SENSE1 3 26 SW1 V 1 24 BOOST1 4 25 BOOST1 OSENSE1 V OSENSE1 PLLFLTR 2 23 V IN PLLFLTR 5 24 V IN PLLIN 3 22 BG1 PLLIN 6 23 BG1 FCB 4 21 EXTV CC 7 EXTV FCB 22 CC 33 I 5 20 INTV TH1 CC I 8 21 INTV TH1 CC SGND 6 19 PGND 9 20 PGND SGND 3.3V 7 18 BG2 OUT 3.3V 10 19 BG2 OUT I 8 17 BOOST2 TH2 I 11 18 BOOST2 TH2 9 10 11 12 13 14 15 16 12 SW2 V 17 OSENSE2 SENSE2 13 16 TG2 + 14 15 RUN/SS2 SENSE2 G PACKAGE UH PACKAGE 28-LEAD PLASTIC SSOP 32-LEAD (5mm 5mm) PLASTIC QFN T = 125C, = 90C/W - SINGLE LAYER BOARD T = 125C, = 34C/W JMAX JA JMAX JA 68 C/W - 4 LAYER EXPOSED PAD IS SGND (MUST BE SOLDERED TO PCB) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3728EG PBF LTC3728EG TRPBF LTC3728EG 28-Lead Plastic SSOP 40C to 85C LTC3728IG PBF LTC3728IG TRPBF LTC3728IG 28-Lead Plastic SSOP 40C to 85C LTC3728EUH PBF LTC3728EUH TRPBF 3728 32-Lead (5mm 5mm) Plastic QFN 40C to 85C LTC3728IUH PBF LTC3728IUH TRPBF 3728 32-Lead (5mm 5mm) Plastic QFN 40C to 85C LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3728EG LTC3728EG TR LTC3728EG 28-Lead Plastic SSOP 40C to 85C LTC3728IG LTC3728IG TR LTC3728IG 28-Lead Plastic SSOP 40C to 85C LTC3728EUH LTC3728EUH TR 3728 32-Lead (5mm 5mm) Plastic QFN 40C to 85C LTC3728IUH LTC3728IUH TR 3728 32-Lead (5mm 5mm) Plastic QFN 40C to 85C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. *The temperature grade is identi ed by a label on the shipping container. 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