LT3991/LT3991-3.3/LT3991-5 55V, 1.2A Step-Down Regulator with 2.8A Quiescent Current Fea T Descrip T n Ultralow Quiescent Current: The LT 3991 is an adjustable frequency monolithic buck 2.8A I Regulating 12V to 3.3V switching regulator that accepts a wide input voltage range Q IN OUT n Fixed Output Voltages: 3.3V, 5V up to 55V. Low quiescent current design consumes only 2.1A I Regulating 12V 2.8A of supply current while regulating with no load. Low Q IN n Low Ripple Burst Mode Operation: ripple Burst Mode operation maintains high efficiency at Output Ripple < 15mV low output currents while keeping the output ripple below P-P n Wide Input Voltage Range: 4.3V to 55V 15mV in a typical application. An internally compensated n 1.2A Maximum Output Current current mode topology is used for fast transient response n Adjustable Switching Frequency: 200kHz to 2MHz and good loop stability. A high efficiency 0.44 switch n Synchronizable Between 250kHz to 2MHz is included on the die along with a boost Schottky diode n Fast Transient Response and the necessary oscillator, control and logic circuitry. n Accurate 1V Enable Pin Threshold An accurate 1V threshold enable pin can be used to shut n Low Shutdown Current: I = 700nA down the LT3991, reducing the input supply current to Q n Power Good Flag 700nA. A capacitor on the SS pin provides a controlled n Soft-Start CapabilityV inrush current (soft-start). A power good flag signals n Internal Compensation when V reaches 91% of the programmed output volt- OUT n Saturating Switch Design: 0.44 On-Resistance age. The LT3991 is available in small 10-pin MSOP and n Output Voltage: 1.19V to 30V 3mm 3mm DFN packages with exposed pads for low n Small Thermally Enhanced 10-Pin MSOP Package thermal resistance. and (3mm 3mm) DFN Packages L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. a T n Automotive Battery Regulation n Power for Portable Products n Industrial Supplies No Load Supply Current Typical a T 3.0 OUTPUT IN REGULATION 3.3V Step Down Converter V IN 4.3V TO 55V 2.5 V IN EN./UVLO BOOST OFF ON LT3991-5 0.47F 12H 2.0 PG SW LT3991-3.3 SS LT3991-3.3 4.7F RT 1.5 BD V OUT 118k 3.3V V OUT SYNC GND 1.2A 47F 1.0 5 10 15 30 35 40 45 50 55 20 25 3991 TA01a INPUT VOLTAGE (V) f = 400kHz 3991 G06 3991fa 1 INPUT CURRENT (A) ion pplica ions pplica ion uresLT3991/LT3991-3.3/LT3991-5 a Te Maxi Mu M r a T (Note 1) V , EN Voltage .........................................................55V Operating Junction Temperature Range (Note 2) IN BOOST Pin Voltage ...................................................75V LT3991E ............................................. 40C to 125C BOOST Pin Above SW Pin .........................................30V LT3991I .............................................. 40C to 125C FB, V , RT, SYNC, SS Voltage .................................6V Storage Temperature Range .............. 65C to 150C OUT PG, BD Voltage .........................................................30V Lead Temperature (Soldering, 10 sec) Boost Diode Current .................................................... 1A (MSE Only) .......................................................300C p in c F T LT3991 LT3991 LT3991-3.3, LT3991-5 TOP VIEW TOP VIEW TOP VIEW BD 1 10 SYNC BD 1 10 SYNC BD 1 10 SYNC BOOST 9 PG 2 BOOST 2 9 PG BOOST 2 9 PG 11 11 11 3 SW 3 8 RT SW 3 8 RT SW 8 RT GND GND GND V 4 7 SS V 4 7 SS IN IN V 4 7 SS IN EN 5 6 FB EN 5 6 V OUT EN 5 6 FB MSE PACKAGE MSE PACKAGE 10-LEAD PLASTIC MSOP 10-LEAD PLASTIC MSOP DD PACKAGE = 45C, = 10C/W = 45C, = 10C/W JA JC JA JC 10-LEAD (3mm 3mm) PLASTIC DFN EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB = 45C, = 10C/W JA JC EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB o r Der i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3991EDD PBF LT3991EDD TRPBF LFJR 40C to 125C 10-Lead (3mm 3mm) Plastic DFN LT3991IDD PBF LT3991IDD TRPBF LFJR 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3991EMSE PBF LT3991EMSE TRPBF LTFJS 10-Lead Plastic MSOP 40C to 125C LT3991IMSE PBF LT3991IMSE TRPBF LTFJS 10-Lead Plastic MSOP 40C to 125C LT3991EMSE-3.3 PBF LT3991EMSE-3.3 TRPBF LTFRS 10-Lead Plastic MSOP 40C to 125C LT3991IMSE-3.3 PBF LT3991IMSE-3.3 TRPBF LTFRS 10-Lead Plastic MSOP 40C to 125C LT3991EMSE-5 PBF LT3991EMSE-5 TRPBF LTFRV 10-Lead Plastic MSOP 40C to 125C LT3991IMSE-5 PBF LT3991IMSE-5 TRPBF LTFRV 10-Lead Plastic MSOP 40C to 125C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: