LTC3727A-1 High Ef ciency, 2-Phase Synchronous Step-Down Switching Regulators FEATURES DESCRIPTION n Wide Output Voltage Range: 0.8V V 14V The LTC 3727A-1 is a high performance dual step-down OUT n Out-of-Phase Controllers Reduce Required Input switching regulator controller that drives all N-channel Capacitance and Power Supply Induced Noise synchronous power MOSFET stages. A constant frequency n OPTI-LOOP Compensation Minimizes C current mode architecture allows phase-lockable frequency OUT n 1% Output Voltage Accuracy of up to 550kHz. Power loss and noise due to the ESR of n Power Good Output Voltage Monitor the input capacitors are minimized by operating the two n Phase-Lockable Fixed Frequency 250kHz to 550kHz controller output stages out of phase. n Dual N-Channel MOSFET Synchronous Drive The LTC3727A-1 is an improved version of the LTC3727 n Wide V Range: 4V to 36V Operation IN family of parts. It has smaller output ripple while in the n Very Low Dropout Operation: 99% Duty Cycle drop-out condition and shorter minimum on-time. n Adjustable Soft-Start Current Ramping n OPTI-LOOP compensation allows the transient response to Foldback Output Current Limiting n be optimized over a wide range of output capacitance and Output Overvoltage Protection n ESR values. There is a precision 0.8V reference and a power Low Shutdown I : 20A Q n good output indicator. A wide 4V to 30V (36V maximum) Selectable Constant Frequency or Burst Mode input supply range encompasses all battery chemistries. Operation n Small 28-Lead SSOP Package A RUN/SS pin for each controller provides soft-start. Current foldback limits MOSFET heat dissipation during short-circuit APPLICATIONS conditions. Output overvoltage protection circuitry protects n Telecom Systems the controller until V returns to normal. OUT n Automotive Systems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. n Battery-Operated Digital Devices All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6304066, 5705919. TYPICAL APPLICATION V IN 18V TO 28V + 22F 1F 50V 4.7F CERAMIC CERAMIC V PGOOD INTV IN CC M1 M3 TG1 TG2 0.1F 8H BOOST1 BOOST2 15H 0.1F SW1 SW2 LTC3727A-1 M2 M4 BG1 BG2 PLLIN PGND + + SENSE1 SENSE2 1000pF 1000pF 0.015 0.015 SENSE2 SENSE1 V V OUT1 OUT2 5V V V 12V OSENSE1 OSENSE2 5A 105k 280k 4A I I TH1 TH2 1% 1% 56F 220pF 220pF RUN/SS1 SGND RUN/SS2 + 47F 20k 20k 15V 6V 1% SP 1% 15k 15k SP 0.1F 0.1F M1, M2, M3, M4: FDS6680A 3727 F01 Figure 1. High Ef ciency Dual 12V/5V Step-Down Converter 3727a1fa 1 +LTC3727A-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Input Supply Voltage (V ) ......................... 36V to 0.3V IN RUN/SS1 1 28 PGOOD Top Side Driver Voltages + SENSE1 2 27 TG1 BOOST1, BOOST2 .................................. 42V to 0.3V SENSE1 3 26 SW1 Switch Voltage (SW1, SW2) ......................... 36V to 5V V 4 25 BOOST1 OSENSE1 INTV , EXTV , (BOOST1-SW1), CC CC PLLFLTR 5 24 V IN (BOOST2-SW2) ......................................... 8.5V to 0.3V PLLIN 6 23 BG1 RUN/SS1, RUN/SS2, PGOOD ...................... 7V to 0.3V FCB 7 22 EXTV CC + + SENSE1 , SENSE2 , SENSE1 , I 8 21 INTV CC TH1 SENSE2 Voltages ..................................... 14V to 0.3V SGND 9 20 PGND PLLIN, PLLFLTR, FCB Voltages ............ INTV to 0.3V 3.3V 10 19 BG2 CC OUT I 11 18 BOOST2 I , I , V , V Voltages ... 2.7V to 0.3V TH2 TH1 TH2 OSENSE1 OSENSE2 V 12 17 SW2 Peak Output Current <10s (TG1, TG2, BG1, BG2) .....3A OSENSE2 SENSE2 13 16 TG2 INTV Peak Output Current ................................. 50mA CC + SENSE2 14 15 RUN/SS2 Operating Temperature Range (Note 2).... 40C to 85C Junction Temperature (Note 3) ............................. 125C G PACKAGE 28-LEAD PLASTIC SSOP Storage Temperature Range ................... 65C to 150C T = 125C, = 95C/W JMAX JA Lead Temperature (Soldering, 10 sec) .................. 300C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3727AEG-1 PBF LTC3727AEG-1 TRPBF LTC3727AEG-1 28-Lead Plastic SSOP 40C to 85C LTC3727AIG-1 PBF LTC3727AIG-1 TRPBF LTC3727AIG-1 28-Lead Plastic SSOP 40C to 85C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3727AEG-1 LTC3727AEG-1 TR LTC3727AEG-1 28-Lead Plastic SSOP 40C to 85C LTC3727AIG-1 LTC3727AIG-1 TR LTC3727AIG-1 28-Lead Plastic SSOP 40C to 85C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. For more information on lead free part marking, go to: