POWER LOSS (mW) LTC3850/LTC3850-1 Dual, 2-Phase Synchronous Step-Down Switching Controller FEATURES DESCRIPTION n Dual, 180 Phased Controllers Reduce Required The LTC 3850 is a high performance dual synchronous Input Capacitance and Power Supply Induced Noise step-down switching regulator controller that drives all n High Efficiency: Up to 95% N-channel power MOSFET stages. A constant-frequency n R or DCR Current Sensing current mode architecture allows a phase-lockable fre- SENSE n 1% 0.8V Output Voltage Accuracy quency of up to 780kHz. Power loss and supply noise are n Phase-Lockable Fixed Frequency 250kHz to 780kHz minimized by operating the two controller output stages n Supports Pre-Biased Output out of phase. n Dual N-Channel MOSFET Synchronous Drive OPTI-LOOP compensation allows the transient response n Wide V Range: 4V to 24V (30V for LTC3850I) IN to be optimized over a wide range of output capacitance Operation and ESR values. The LTC3850 features a precision 0.8V n Adjustable Soft-Start Current Ramping or Tracking reference and a power good output indicator. A wide 4V n Foldback Output Current Limiting to 24V (28V maximum/30V for LTC3850I) input supply n Power Good Output Voltage Monitor range encompasses most battery chemistries and inter- n 28-Pin 4mm 4mm, 4mm 5mm QFN and Narrow mediate bus voltages. SSOP Packages n Independent TK/SS pins for each controller ramp the AEC-Q100 Qualified for Automotive Applications output voltages during start-up. Current foldback limits APPLICATIONS MOSFET heat dissipation during short-circuit conditions. The MODE/PLLIN pin selects among Burst Mode opera- n Notebook and Palmtop Computers tion, pulse-skipping mode, or continuous inductor cur- n Portable Instruments rent mode and allows the IC to be synchronized to an n Battery-Operated Digital Devices externalclock. n DC Power Distribution Systems All registered trademarks and trademarks are the property of their respective owners. Protected The LTC3850 is available in low profile 28-pin 4mm by U.S. patents, including 5481178, 5705919, 5929620, 6100678, 6144194, 6177787, 4mm, 4mm 5mm QFN and narrow SSOP packages. 6304066, 6580258. TYPICAL APPLICATION High Efficiency Dual 3.3V/2.5V Step-Down Converter Efficiency V IN 7V TO 100 10000 22F V = 12V IN 24V 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 2.2k BG1 BG2 70 2.2k 500kHz MODE/PLLIN PGND 100 65 I FREQ/PLLFLTR POWER LOSS LIM 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 38501 TA01b TK/SS1 SGND TK/SS2 100F 100F 20k 20k 15k 10k 15k 6V 0.1F 0.1F 6V 38501 TA01 Rev. D 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LTC3850/LTC3850-1 ABSOLUTE MAXIMUM RATINGS (Note 1) + + Input Supply Voltage (V ) ......................... 28V to 0.3V SENSE1 , SENSE2 , SENSE1 , IN Input Supply Voltage (V ), SENSE2 Voltages .................................... 5.5V to 0.3V IN LTC3850I Only .......................................30V to 0.3V MODE/PLLIN, I ,TK/SS1,TK/SS2, FREQ/PLLFLTR LIM Input Supply Transient Voltage (V ) < 500ms, with Voltages ................................................INTV to 0.3V IN CC INTV 5V, LTC3850I Only .................34V to 0.3V I , I , V , V Voltages ................. 2.7V to 0.3V CC TH1 TH2 FB1 FB2 Top Side Driver Voltages INTV Peak Output Current ................................100mA CC BOOST1, BOOST2 ..................................34V to 0.3V Operating Temperature Range (Note 2)....40C to 85C Switch Voltage (SW1, SW2) ..........................28V to 5V Junction Temperature (Note 3) ............................. 125C Switch Voltage (SW1, SW2), Storage Temperature Range .................. 65C to 125C LTC3850I Only ..........................................30V to 5V Lead Temperature (Soldering, 10 sec) INTV , RUN1, RUN2, PGOOD, EXTV , (GN Package) ....................................................300C CC CC (BOOST1-SW1), (BOOST2-SW2) ................. 6V to 0.3V PIN CONFIGURATION TOP VIEW TOP VIEW 1 28 FREQ/PLLFLTR RUN1 + SENSE1 2 27 MODE/PLLIN 3 26 SW1 SENSE1 TK/SS1 4 25 TG1 28 27 26 25 24 23 22 I 5 24 BOOST1 TH1 TK/SS1 1 21 BOOST1 6 23 BG1 V FB1 I 2 20 BG1 TH1 SGND 7 22 V IN V V 3 19 FB1 IN 8 21 INTV V CC FB2 V 4 29 18 INTV FB2 CC I 9 20 BG2 TH2 I 5 17 BG2 TH2 TK/SS2 10 19 PGND TK/SS2 6 16 PGND 11 18 BOOST2 SENSE2 SENSE2 7 15 BOOST2 + SENSE2 12 17 TG2 8 9 10 11 12 13 14 13 16 SW2 RUN2 I (EXTV )* 14 15 PGOOD LIM CC GN PACKAGE UF PACKAGE 28-LEAD NARROW PLASTIC SSOP 28-LEAD (4mm 4mm) PLASTIC QFN T = 125C, = 95C/W T = 125C, = 37C/W, = 2.6C/W JMAX JA JMAX JA JC *PIN 14 = I FOR LTC3850GN, EXTV FOR LTC3850GN-1 EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB LIM CC TOP VIEW 28 27 26 25 24 23 SENSE1 1 22 BOOST1 TK/SS1 2 21 BG1 ITH1 3 20 VIN VFB1 4 19 INTV CC 29 VFB2 5 18 BG2 ITH2 6 17 PGND TK/SS2 7 16 BOOST2 SENSE2 8 15 TG2 9 10 11 12 13 14 UFD PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN T = 125C, = 34C/W, EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB JMAX JA Rev. D 2 For more information www.analog.com + + SENSE2 SENSE1 RUN2 RUN1 ILIM FREQ/PLLFLTR EXTV MODE/PLLIN CC PGOOD SW1 SW2 TG1 + SENSE2 SENSE1 + RUN2 SENSE1 I RUN1 LIM EXTV FREQ/PLLFLTR CC PGOOD MODE/PLLIN SW2 SW1 TG2 TG1