POWER LOSS (mW) LTC3850-2 Dual, 2-Phase Synchronous Step-Down Switching Controller FEATURES DESCRIPTION n Dual, 180 Phased Controllers Reduce Required The LTC 3850-2 is a high performance dual synchronous Input Capacitance and Power Supply Induced Noise step-down switching regulator controller that drives all n High Ef ciency: Up to 95% N-channel power MOSFET stages. A constant-frequency n R or DCR Current Sensing current mode architecture allows a phase-lockable SENSE n 1% 0.8V Output Voltage Accuracy frequency of up to 780kHz. Power loss and supply noise n Phase-Lockable Fixed Frequency 250kHz to 780kHz are minimized by operating the two controller output n Supports Pre-Biased Output stages out of phase. n Dual N-Channel MOSFET Synchronous Drive OPTI-LOOP compensation allows the transient response n Wide V Range: 4V to 30V Operation IN to be optimized over a wide range of output capacitance n Adjustable Soft-Start Current Ramping or Tracking and ESR values. The LTC3850-2 features a precision 0.8V n Foldback Output Current Limiting reference and a power good output indicator. A wide 4V n Output Overvoltage Protection to 30V input supply range encompasses most battery n Power Good Output Voltage Monitor chemistries and intermediate bus voltages. n 28-Pin Narrow SSOP Package Independent TK/SS pins for each controller ramp the APPLICATIONS output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit condi- n Notebook and Palmtop Computers tions. The MODE/PLLIN pin selects among Burst Mode n Portable Instruments operation, pulse-skipping mode, or continuous inductor n Battery-Operated Digital Devices current mode and allows the IC to be synchronized to an n DC Power Distribution Systems external clock. L, LT, LTC, LTM, OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. The LTC3850-2 is identical to the LTC3850-1, except they Patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 6304066, 6580258. have different pin assignments. TYPICAL APPLICATION High Ef ciency Dual 3.3V/2.5V Step-Down Converter Ef ciency V IN 100 10000 7V TO 22F V = 12V IN 26V 4.7F 50V 95 V = 3.3V EFFICIENCY OUT V PGOOD INTV IN CC 90 TG1 TG2 0.1F 0.1F 85 1000 BOOST1 BOOST2 2.2H 2.2H 80 SW1 SW2 75 LTC3850-2 2.2k BG1 BG2 70 2.2k 500kHz MODE/PLLIN PGND 100 65 EXT FREQ/PLLFLTR POWER LOSS VCC 60 + + SENSE1 SENSE2 55 0.1F RUN1 0.1F RUN2 V SENSE1 SENSE2 OUT1 V OUT2 50 10 3.3V V V 2.5V FB1 FB2 10 100 1000 10000 5A 63.4k 43.2k 5A I I TH1 TH2 LOAD CURRENT (mA) 220pF 10nF 220pF 38502 TA01b TK/SS1 SGND TK/SS2 100F 100F 20k 20k 15k 10k 15k 6V 0.1F 0.1F 6V 38502 TA01 38502f 1 EFFICIENCY (%)LTC3850-2 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Input Supply Voltage (V ) .........................30V to 0.3V TOP VIEW IN Input Supply Transient Voltage (V ) < 500ms, with 1 FREQ/PLLFLTR RUN1 28 IN + INTV 5V ...........................................34V to 0.3V 2 MODE/PLLIN SENSE1 27 CC 3 SW1 Top Side Driver Voltages SENSE1 26 4 TG1 V 25 BOOST1, BOOST2 ..................................34V to 0.3V FB1 5 BOOST1 TK/SS1 24 Switch Voltage (SW1, SW2) .........................30V to 5V 6 BG1 I 23 TH1 INTV , RUN1, RUN2, PGOOD, EXTV , CC CC 7 V SGND 22 IN (BOOST1-SW1), (BOOST2-SW2) .................6V to 0.3V 8 INTV I 21 + + TH2 CC SENSE1 , SENSE2 , SENSE1 , 9 BG2 TK/SS2 20 SENSE2 Voltages .....................................5.5V to 0.3V 10 PGND V 19 FB2 MODE/PLLIN, TK/SS1,TK/SS2, FREQ/PLLFLTR 11 BOOST2 SENSE2 18 Voltages ................................................ INTV to 0.3V + CC 12 TG2 SENSE2 17 I , I , V , V Voltages ..................2.7V to 0.3V TH1 TH2 FB1 FB2 13 SW2 RUN2 16 INTV Peak Output Current ................................100mA 14 PGOOD CC EXTV 15 CC Operating Temperature Range (Note 2)....40C to 85C GN PACKAGE Junction Temperature (Note 3) ............................. 125C 28-LEAD NARROW PLASTIC SSOP Storage Temperature Range ...................65C to 125C T = 125C, = 95C/W JMAX JA Lead Temperature (Soldering, 10 sec) (GN Package) .................................................... 300C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3850IGN-2 PBF LTC3850IGN-2 TRPBF LTC3850GN-2 28-Lead Narrow Plastic SSOP 40C to 85C Consult LTC Marketing for parts speci ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based nish parts. For more information on lead free part marking, go to: