POWER LOSS (mW) LTC3868 Low I , Dual Q 2-Phase Synchronous Step-Down Controller FEATURES DESCRIPTION n Low Operating I : 170A (One Channel On) The LTC 3868 is a high performance dual step-down Q n switching regulator controller that drives all N-channel Wide Output Voltage Range: 0.8V V 14V OUT n synchronous power MOSFET stages. A constant frequency Wide V Range: 4V to 24V IN n current mode architecture allows a phase-lockable fre- R or DCR Current Sensing SENSE n quency of up to 850kHz. Power loss and noise due to the Out-of-Phase Controllers Reduce Required Input input capacitor ESR are minimized by operating the two Capacitance and Power Supply Induced Noise n controller outputs out of phase. OPTI-LOOP Compensation Minimizes C OUT n Phase-Lockable Frequency (75kHz to 850kHz) The 170A no-load quiescent current extends operating life in n Programmable Fixed Frequency (50kHz to 900kHz) battery-powered systems. OPTI-LOOP compensation allows n Selectable Continuous, Pulse-Skipping or the transient response to be optimized over a wide range of Burst Mode Operation at Light Loads output capacitance and ESR values. The LTC3868 features a n Very Low Dropout Operation: 99% Duty Cycle precision 0.8V reference and a power good output indicator. A n Adjustable Output Voltage Soft-Start wide 4V to 24V input supply range encompasses a wide range n Power Good Output Voltage Monitor of intermediate bus voltages and battery chemistries. n Output Overvoltage Protection Independent soft-start pins for each controller ramp the n Output Latchoff Protection During Short Circuit output voltages during start-up. Current foldback limits n Low Shutdown I : 8A Q MOSFET heat dissipation during short-circuit conditions. n Internal LDO Powers Gate Drive from V or EXTV IN CC The output short-circuit latchoff feature further protects n No Current Foldback During Start-Up the circuit in short-circuit conditions. n Small 5mm 5mm QFN Package For a leaded 28-lead SSOP package with a xed current APPLICATIONS limit and one PGOOD output, without phase modulation n Notebook and Palmtop Computers or a clock output, see the LTC3868-1 data sheet. n Portable Instruments L, LT, LTC, LTM, Burst Mode, OPTI-LOOP, PolyPhase, Module, Linear Technology and the Linear logo are registered trademarks and No R and UltraFast are trademarks of Linear Technology SENSE n Battery Operated Digital Devices Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. n Distributed DC Power Systems TYPICAL APPLICATION High Ef ciency Dual 8.5V/3.3V Step-Down Converter V IN Ef ciency and Power Loss 9V TO 24V 22F vs Load Current 4.7F 50V V INTV 100 10000 IN CC TG1 TG2 90 0.1F 0.1F BOOST1 BOOST2 3.3H 7.2H 80 1000 EFFICIENCY SW1 SW2 70 BG1 BG2 60 100 LTC3868 POWER LOSS PGND 50 + + SENSE1 SENSE2 40 10 30 0.007 0.01 20 1 V SENSE2 V SENSE1 OUT2 OUT1 V = 12V IN 8.5V 3.3V V V FB1 FB2 10 V = 3.3V OUT 3.5A 5A 62.5k 193k I I FIGURE 12 CIRCUIT TH1 TH2 0 0.1 150F 680pF 680pF 150F SS1 SGND SS2 0.0001 0.001 0.01 0.1 1 10 20k 20k 15k OUTPUT CURRENT (A) 15k 0.1F 0.1F 3868 TA01b 3868 TA01 3868fd 1 EFFICIENCY (%)LTC3868 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW Input Supply Voltage (V ) ......................... 0.3V to 28V IN Topside Driver Voltages BOOST1, BOOST2 ................................. 0.3V to 34V 32 31 30 29 28 27 26 25 Switch Voltage (SW1, SW2) ........................ 5V to 28V SENSE1 1 24 BOOST1 PLLIN/MODE FREQ 2 23 BG1 (BOOST1-SW1), (BOOST2-SW2) ................ 0.3V to 6V PHASMD 3 22 V IN RUN1, RUN2 ................................................ 0.3V to 8V CLKOUT 4 21 PGND 33 SGND PLLIN/MODE 5 20 EXTV Maximum Current Sourced into Pin from CC SGND INTV 6 19 CC Source >8V ......................................................100A + + RUN1 7 18 BG2 SENSE1 , SENSE2 , SENSE1 RUN2 8 17 BOOST2 SENSE2 Voltages ...................................... 0.3V to 16V 9 10 11 12 13 14 15 16 FREQ Voltages ..................................... 0.3V to INTV CC I , PHASMD Voltages ....................... 0.3V to INTV LIM CC EXTV ...................................................... 0.3V to 14V CC UH PACKAGE 32-LEAD (5mm s 5mm) PLASTIC QFN I , I ,V , V Voltages ...................... 0.3V to 6V TH1 TH2 FB1 FB2 T = 125C, = 34C/W JMAX JA PGOOD1, PGOOD2 Voltages ....................... 0.3V to 6V EXPOSED PAD (PIN 33) IS SGND, MUST BE SOLDERED TO PCB SS1, SS2, INTV Voltages ......................... 0.3V to 6V CC Operating Temperature Range (Note 2) ... 40C to 85C Junction Temperature (Note 3) ............................. 125C Storage Temperature Range ................... 65C to 150C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3868EUH PBF LTC3868EUH TRPBF 3868 32-Lead (5mm 5mm) Plastic QFN 40C to 85C LTC3868IUH PBF LTC3868IUH TRPBF 3868 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.Consult LTC Marketing for information on non-standard lead based nish parts. For more information on lead free part marking, go to: