LTC3879 Fast, Wide Operating Range No R SENSE Step-Down Controller FEATURES DESCRIPTION n The LTC 3879 is a synchronous step-down switching Wide V Range: 4V to 38V IN n regulator controller optimized for high switching frequency 1% 0.6V Voltage Reference n and fast transient response. The constant on-time valley Extremely Fast Transient Response n current mode architecture allows for a wide input range, t : 43ns ON(MIN) n including very low duty factor operation. No external sense No R Valley Current Mode Control SENSE n resistor or slope compensation is required. System ex- Stable with Low ESR Ceramic C OUT n ibility is offered through a user-programmable soft-start pin Supports Smooth Start-Up in Pre-Biased Output n and independent RUN pin. The voltage ramping soft-start Optimized for High Step-Down Ratios n function can be programmed with a capacitor or made to Adjustable Output Voltage Soft-Start or Tracking n track an external reference source. Power Good Output Voltage Monitor n Dual N-Channel MOSFET Synchronous Drive Operating frequency is set by an external resistor and n Adjustable Switching Frequency compensated for variations in V to offer excellent line IN n Programmable Current Limit with Foldback stability. Discontinuous mode operation provides high n Output Overvoltage Protection ef ciency during light load conditions. A forced continu- n 16-Pin MSOP and 3mm 3mm QFN Packages ous control pin allows the user to reduce noise and RF interference. Safety features include output overvoltage APPLICATIONS protection and programmable current limit with foldback. n The current limit is user programmable. Distributed Power Systems n Embedded Computing The LTC3879 allows operation from 4V to 38V at the input n Communications Infrastructure and from 0.6V to 90% V at the output. The LTC3879 is IN L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. available in a small 16-pin thermally enhanced MSOP or No R is a trademark of Linear Technology Corporation. SENSE All other trademarks are the property of their respective owners. 3mm 3mm QFN packages. Protected by U.S. Patents, including 5481178, 6100678, 6580258, 5847554, 6304066. TYPICAL APPLICATION High Ef ciency Step-Down Converter Ef ciency vs Load Current 432k 100 0.1F RUN I ON 90 DISCONTINUOUS V IN TRACK/SS V IN MODE 4.5V TO 28V 80 220pF TG RJK0305 10F 27k LTC3879 70 I SW 0.56H TH V OUT CONTINUOUS SGND BOOST 1.2V 60 MODE 15A MODE 50 0.22F INTV 330F CC 40 s 2 RJK0330 BG 4.7F 30 PGND PGOOD V = 12V IN 20 V = 1.2V OUT 10k 10 SW FREQ = 400kHz V V RNG FIGURE 10 CIRCUIT FB 0 10k 0.01 0.1 1 10 100 LOAD CURRENT (A) 3879 TA01a 3879 TA01b 3879f 1 EFFICIENCY (%)LTC3879 ABSOLUTE MAXIMUM RATINGS (Note 1) Input Supply Voltage (V ) ......................... 0.3V to 40V V , I Voltages ....................................... 0.3V to 2.7V IN FB TH I Voltage ................................................. 0.3V to 40V Operating Temperature Range (Note 4)....40C to 85C ON BOOST Voltage .......................................... 0.3V to 46V Junction Temperature (Note 2) ............................. 125C SW Voltage ................................................... 5V to 40V Storage Temperature Range ...................65C to 150C INTV , (BOOST-SW), TRACK/SS, RUN, Lead Temperature (Soldering, 10 sec) CC PGOOD Voltages .......................................... 0.3V to 6V MSOP Only .......................................................300C MODE, V Voltages ................0.3V to INTV + 0.3V RNG CC PIN CONFIGURATION TOP VIEW TOP VIEW 16 15 14 13 1 TRACK/SS 16 BOOST PGOOD 2 15 TG TRACK/SS 1 12 BG 3 V 14 SW RNG PGOOD 2 11 INTV MODE 4 13 PGND CC 17 17 5 I 12 BG TH V 3 10 V RNG IN SGND 6 11 INTV CC 7 I 10 V MODE 4 9 RUN ON IN V 8 9 RUN FB 5 6 7 8 MSE PACKAGE 16-LEAD PLASTIC MSOP T = 125C, = 40C/W JMAX JA UD PACKAGE EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB 16-LEAD (3mm s 3mm) PLASTIC QFN T = 125C, = 68C/W, = 4.2C/W JMAX JA JC EXPOSED PAD (PIN 17) IS SGND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3879EMSE PBF LTC3879EMSE TRPBF 3879 16-Lead Plastic MSOP 40C to 85C (Note 4) LTC3879IMSE PBF LTC3879IMSE TRPBF 3879 16-Lead Plastic MSOP 40C to 85C (Note 4) LTC3879EUD PBF LTC3879EUD TRPBF LDTM 40C to 85C (Note 4) 16-Lead (3mm 3mm) Plastic QFN LTC3879IUD PBF LTC3879IUD TRPBF LDTM 40C to 85C (Note 4) 16-Lead (3mm 3mm) Plastic QFN 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: