LT3685 36V, 2A, 2.4MHz Step-Down Switching Regulator FEATURES DESCRIPTION Wide Input Range: The LT 3685 is an adjustable frequency (200kHz to 2.4MHz) Operation From 3.6V to 36V monolithic step-down switching regulator that accepts Overvoltage Lockout Protects Circuit through input voltages up to 38V operating and 60V maximum. An 60V Transients internal overvoltage protection circuit turns off the power 2A Maximum Output Current switch when V is above 38V typical (36V minimum) which IN Adjustable Switching Frequency: 200kHz to 2.4MHz then allows the part to safely withstand 60V transients. A Low Shutdown Current: I < 1A high ef ciency 0.25 switch is included on the die along Q Integrated Boost Diode with a boost Schottky diode and the necessary oscillator, Synchronizable Between 250kHz to 2MHz control, and logic circuitry. Current mode topology is Power Good Flag used for fast transient response and good loop stability. Saturating Switch Design: 0.25 On-Resistance The LT3685s high operating frequency allows the use of 0.790V Feedback Reference Voltage small, low cost inductors and ceramic capacitors result- Output Voltage: 0.79V to 20V ing in low output ripple while keeping total solution size Soft-Start Capability to a minimum. The low current shutdown mode reduces Small 10-Pin Thermally Enhanced MSOP and input supply current to less than 1A while a resistor and (3mm 3mm) DFN Packages capacitor on the RUN/SS pin provide a controlled output voltage ramp (soft-start). A power good ag signals when V reaches 89% of the programmed output voltage. The OUT APPLICATIONS LT3685 is available in 10-Pin MSOP and 3mm 3mm DFN Automotive Battery Regulation packages with exposed pads for low thermal resistance. Set Top Box , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Distributed Supply Regulation Burst Mode is a registered trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Industrial Supplies Wall Transformer Regulation TYPICAL APPLICATION 3.3V Step-Down Converter Ef ciency 100 V V IN OUT 4.5V TO 36V 3.3V TRANSIENT 2A V = 5V OUT V BD IN TO 60V 90 RUN/SS BOOST OFF ON V = 3.3V OUT 80 0.47F 4.7H 14k V SW C LT3685 4.7F 70 R T 470pF PG 60 316k V = 12V IN 40.2k SYNC FB GND L = 5.6H F = 800 kHz 50 100k 22F 0 0.5 1.0 1.5 2 LOAD CURRENT (A) 3685 TA01b 3685 TA01 3685fb 1 EFFICIENCY (%)LT3685 (Note 1) ABSOLUTE MAXIMUM RATINGS Operating Junction Temperature Range (Note 2) V , RUN/SS Voltage (Note 5) ...................................60V IN LT3685E ............................................. 40C to 125C BOOST Pin Voltage ...................................................56V LT3685I .............................................. 40C to 125C BOOST Pin Above SW Pin .........................................30V Storage Temperature Range ................... 65C to 150C FB, RT, V Voltage .......................................................5V C Lead Temperature (Soldering, 10 sec) PG, BD, SYNC Voltage ..............................................30V (MSE Only) ....................................................... 300C PIN CONFIGURATION TOP VIEW TOP VIEW BD 1 10 R T BD 1 10 R T BOOST 2 9 V C BOOST 2 9 V C 11 SW 3 11 8 FB SW 3 8 FB V 4 7 PG IN V 4 7 PG IN RUN/SS 5 6 SYNC RUN/SS 5 6 SYNC MSE PACKAGE 10-LEAD PLASTIC MSOP DD PACKAGE = 45C/W, = 10C/W JA JC 10-LEAD (3mm s 3mm) PLASTIC DFN EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB = 45C/W, = 10C/W JA JC EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3685EDD PBF LT3685EDD TRPBF LCYG 40C to 125C 10-Lead (3mm 3mm) Plastic DFN LT3685IDD PBF LT3685IDD TRPBF LCYG 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3685EMSE PBF LT3685EMSE TRPBF LTCYF 40C to 125C 10-Lead Plastic MSOP LT3685IMSE PBF LT3685IMSE TRPBF LTCYF 40C to 125C 10-Lead Plastic MSOP 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: