POWER LOSS (mW) LTC3891 Low I , 60V Synchronous Q Step-Down Controller FEATURES DESCRIPTION n Wide V Range: 4V to 60V (65V Abs Max) The LTC 3891 is a high performance step-down switching IN n Low Operating I : 50A regulator DC/DC controller that drives an all N-channel Q n Wide Output Voltage Range: 0.8V V 24V synchronous power MOSFET stage. A constant fre- OUT n R or DCR Current Sensing quency current mode architecture allows a phase-lockable SENSE n Phase-Lockable Frequency (75kHz to 750kHz) frequency of up to 750kHz. n Programmable Fixed Frequency (50kHz to 900kHz) The 50A no-load quiescent current extends operating run n Selectable Continuous, Pulse-Skipping or Low Ripple time in battery-powered systems. OPTI-LOOP compensa- Burst Mode Operation at Light Load tion allows the transient response to be optimized over n Selectable Current Limit a wide range of output capacitance and ESR values. The n Very Low Dropout Operation: 99% Duty Cycle LTC3891 features a precision 0.8V reference and power n Adjustable Output Voltage Soft-Start or Tracking good output indicator. A wide 4V to 60V input supply range n Power Good Output Voltage Monitor encompasses a wide range of intermediate bus voltages n Output Overvoltage Protection and battery chemistries. The output voltage of the LTC3891 n Low Shutdown I : < 14A Q can be programmed between 0.8V to 24V. n Internal LDO Powers Gate Drive from V or EXTV IN CC n The TRACK/SS pin ramps the output voltages during No Current Foldback During Start-Up n start-up. Current foldback limits MOSFET heat dissipation Small 20-Pin 3mm 4mm QFN and TSSOP Packages during short-circuit conditions. The PLLIN/MODE pin se- lects among Burst Mode operation, pulse-skipping mode, APPLICATIONS or continuous conduction mode at light loads. n L, LT, LTC, LTM, OPTI-LOOP, Burst Mode, Linear Technology and the Linear logo are registered Automotive Always-On Systems trademarks of Linear Technology Corporation. All other trademarks are the property of their n Battery Powered Digital Devices respective owners. Patents, including 5481178, 5705919, 6611131, 6498466, 6580258, 7230497. n Distributed DC Power Systems TYPICAL APPLICATION Efficiency and Power Loss vs High Efficiency 3.3V Step-Down Converter Output Current V IN 100 10000 4V TO 60V V = 12V IN 22F V = 3.3V 90 OUT V INTV IN CC LTC3891 1000 80 2.2F 70 TG 100 41.2k 60 FREQ 0.1F 50 BOOST 2200pF 4.7H 10k 8m V OUT 10 40 ITH SW 3.3V 100pF 30 5A 150F BG 20 1 0.1F + 10 TRACK/SS SENSE 0.1 0 0.0001 0.001 0.01 0.1 1 10 100k SENSE OUTPUT CURRENT (A) SGND V 3891 TA01b FB 100k PGOOD INTV CC 31.6k 3891 TA01a 3891fa 1 EFFICIENCY (%)LTC3891 ABSOLUTE MAXIMUM RATINGS (Note 1) ITH, V Voltages ......................................... 0.3V to 6V Input Supply Voltage (V ) ......................... 0.3V to 65V IN FB PGOOD Voltage ............................................ 0.3V to 6V Topside Driver Voltage (BOOST) .................0.3V to 71V TRACK/SS Voltage ....................................... 0.3V to 6V Switch Voltage (SW) ..................................... 5V to 65V Operating Junction Temperature Range (Notes 2, 3) (BOOST-SW) ................................................ 0.3V to 6V LTC3891E, LTC3891I .......................... 40C to 125C RUN ............................................................. 0.3V to 8V LTC3891H .......................................... 40C to 150C Maximum Current Sourced into Pin from LTC3891MP ....................................... 55C to 150C Source > 8V ......................................................100A + Maximum Junction Temperature (Notes 2, 3) SENSE , SENSE Voltages ......................... 0.3V to 28V LTC3891E, LTC3891I ......................................... 125C PLLIN/MODE, INTV Voltages ................... 0.3V to 6V CC LTC3891H, LTC3891MP .................................... 150C I , FREQ Voltages ..............................0.3V to INTV LIM CC Storage Temperature Range .................. 65C to 150C EXTV ...................................................... 0.3V to 14V CC PIN CONFIGURATION TOP VIEW TOP VIEW TRACK/SS 1 20 I LIM 20 19 18 17 FREQ 2 19 V IN PLLIN/MODE 3 18 PGND PLLIN/MODE 1 16 PGND SGND 4 17 EXTV SGND 2 15 EXTV CC CC SGND 3 14 INTV SGND 5 21 16 INTV 21 CC CC SGND SGND RUN 4 13 BG RUN 6 15 BG BOOST SENSE 5 12 SENSE 7 14 BOOST + SENSE 6 11 SW + SENSE 8 13 SW 7 8 9 10 V 9 TG 12 FB ITH 10 11 PGOOD FE PACKAGE 20-LEAD PLASTIC TSSOP UDC PACKAGE 20-LEAD (3mm 4mm) PLASTIC QFN T = 150C, = 38C/W JMAX JA EXPOSED PAD (PIN 21) IS SGND, MUST BE SOLDERED TO PCB T = 150C, = 43C/W JMAX JA EXPOSED PAD (PIN 21) IS SGND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3891EUDC PBF LTC3891EUDC TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 125C LTC3891IUDC PBF LTC3891IUDC TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 125C LTC3891HUDC PBF LTC3891HUDC TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 40C to 150C LTC3891MPUDC PBF LTC3891MPUDC TRPBF LFXV 20-Lead (3mm 4mm) Plastic QFN 55C to 150C 3891fa 2 V FREQ FB TRACK/SS ITH PGOOD I LIM TG V IN