LT3686 37V/1.2A Step-Down Regulator in 3mm 3mm DFN Fe A Description n Wide Input Range: The LT 3686 is a current mode PWM step-down DC/DC Operation from 3.6V to 37V converter with an internal 1.2A power switch, packaged in Overvoltage Lockout Protects Circuit Through 10-lead 3mm 3mm DFN. The wide input range of 3.6V to 55V Transients 37V makes the LT3686 suitable for regulating power from n Low Minimum On-Time: a wide variety of sources, including 24V industrial supplies Converts 16V to 3.3V at 2MHz and automotive batteries. Its high maximum frequency al- IN OUT n 1.2A Output Current lows the use of tiny inductors and capacitors, resulting in n Adjustable Frequency: 300kHz to 2.5MHz a very small solution. Operating frequency above the AM n Constant Switching Frequency at Light Loads band avoids interfering with radio reception, making the n Tracking and Soft-Start LT3686 particularly suitable for automotive applications. n Precision UVLO Cycle-by-cycle current limit and DA current sense provide n Short-Circuit Robust protection against fault conditions. Soft-start and frequency n I in Shutdown <1A Q foldback eliminate input current surge during start-up. An n Internally Compensated optional internal regulated active load at the output via n 10-Lead 3mm 3mm DFN Package the BD pin keeps the LT3686 at full switching frequency at light loads, resulting in low, predictable output ripple Applic A above the audio and AM bands. Internal compensation and an internal boost diode reduce external component count. n Automotive Systems L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks n Battery-Powered Equipment of Linear Technology Corporation. All other trademarks are the property of their respective n owners. Wall Transformer Regulation n Distributed Supply Regulation t Al Applic A 3.3V Step-Down Converter 12V Efficiency (2.1MHz) IN 90 V IN V BD IN 6V TO 37V 80 3.3V OUT 2.2F EN/UVLO BOOST 0.22F 70 5V OUT LT3686 6.8H 60 SW V MODE OUT 3.3V 50 MBRM140 1.2A SS 40 DA 31.6k 10nF RT 30 FB GND 20 10k 22F 15.4k 10 3686 TA01a 0 0 200 400 600 800 1000 1200 (V 6V TO 16V AT 2.1MHz) IN LOAD CURRENT (mA) 3686 TA01b 3686fc 1 EFFICIENCY (%) tion ypic tions turesLT3686 Absolute M A Mu M rA p in c F A (Note 1) TOP VIEW Input Voltage (V ) ....................................................55V IN BOOST Voltage .........................................................55V V 1 10 SW IN BD 9 DA 2 BOOST Pin Above SW Pin .........................................25V 11 FB 3 BOOST 8 GND FB Voltage ...................................................................6V 4 SS 7 MODE EN/UVLO Voltage ......................................................55V RT 5 6 EN/UVLO BD Voltage ................................................................25V DD PACKAGE RT Voltage ..................................................................6V 10-LEAD (3mm 3mm) PLASTIC DFN = 43C/W SS Voltage ...............................................................2.5V JA EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB MODE Voltage .............................................................6V Operating Junction Temperature Range (Note 2) LT3686E ............................................ 40C to 125C LT3686I ............................................. 40C to 125C LT3686H ............................................ 40C to 150C Storage Temperature Range .................. 65C to 150C o r Der i n F MA LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3686EDD PBF LT3686EDD TRPBF LDYC 10-Lead Plastic DFN 40C to 125C LT3686IDD PBF LT3686IDD TRPBF LDYC 10-Lead Plastic DFN 40C to 125C LT3686HDD PBF LT3686HDD TRPBF LDYC 10-Lead Plastic DFN 40C to 150C 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: