POWER LOSS (mW) LT3689/LT3689-5 700mA Step-Down Regulator with Power-On Reset and Watchdog Timer FEATURES DESCRIPTION n Wide Input Range: The LT 3689 is an adjustable frequency (350kHz to 2.2MHz) Operation from 3.6V to 36V monolithic step-down switching regulator with a power-on Overvoltage Lockout Protects Circuits through reset and watchdog timer. The regulator operates from 60V Transients inputs up to 36V and withstands transients up to 60V. Low n 85A I at 12V to 3.3V ripple Burst Mode operation maintains high efficiency at Q IN OUT n Low Ripple Burst Mode Operation Allows Output low output current while keeping output ripple below 15mV Ripple <15mV in a typical application, with input quiescent current of just P-P n Programmable, Defeatable Watchdog Timer with 85A. Shutdown circuitry reduces input supply current to Window or Timeout Control less than 1A while EN/UVLO is pulled low. Using a resis- n Programmable Power-On Reset Timer (POR) tor divider on the EN/UVLO pin provides a programmable n Synchronizable, Adjustable 350kHz to 2.2MHz undervoltage lockout. Current limit, frequency foldback Switching Frequency and thermal shutdown provide fault protection. n 700mA Output Switching Regulator with Internal The reset and watchdog timeout periods are indepen- Power Switch dently adjustable using external capacitors. Tight accuracy n Fixed 5V or Adjustable Output Voltage specifications and glitch immunity ensure reliable reset n 800mV Feedback Voltage operation of a system without false triggering. The open n Programmable Input Undervoltage Lockout with collector RST will pull down if output voltage drops 10% Hysteresis below the programmed value. The watchdog timer is n 16-Pin 3mm 3mm QFN and 16-Pin MSOP Packages pin-selectable for window or timeout modes. In timeout mode, WDO pulls low if too long of a period passes before APPLICATIONS a watchdog transition is detected. In window mode, the LT3689 monitors for WDI falling edges grouped too close n Automotive Electronic Control Units together or too far apart. n Industrial Power Supplies L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION Efficiency 3.3V Regulator with Power-On Reset Timer and Watchdog Timer 90 1000 V = 12V IN V IN V = 3.3V 80 OUT 4.5V TO 36V 2.2F f = 700kHz TRANSIENT TO 60V V EN/UVLO OUT IN 70 L = 12H BST T = 25C A 0.1F 12H 60 100 P 3.3V I/O WDI SW 700mA 50 10pF LT3689 I/O WDO 40 RESET RST DA 316k 30 10 FB C C WDT WDT RT 20 10nF 22F C C GND SYNC POR POR t = 182ms 20.5k 100k WDU 68nF 10 t = 5.9ms WDL t = 157ms f = 700kHz SW RST 0 1 3689 TA01 0.0001 0.001 0.01 0.1 1 LOAD CURRENT (A) 3689 TA01b 3689fe 1 For more information www.linear.com/LT3689 EFFICIENCY (%)LT3689/LT3689-5 ABSOLUTE MAXIMUM RATINGS (Note 1) V , EN/UVLO Voltage (Note 2) .................................60V Operating Junction Temperature Range (Note 3) IN BST Voltage ..............................................................60V LT3689E ............................................ 40C to 125C BST Above SW Voltage .............................................30V LT3689I ............................................. 40C to 125C OUT, WDE Voltage ....................................................30V LT3689H ............................................ 40C to 150C FB, RT, SYNC, W/T, WDI, RST, WDO Voltage ..............6V Storage Temperature Range .................. 65C to 150C C , C Voltage ....................................................3V Lead Temperature (Soldering, 10 sec) WDT POR MSOP ...............................................................300C PIN CONFIGURATION TOP VIEW TOP VIEW 16 15 14 13 WDO 1 16 RST BST 1 12 C WDT C 2 15 WDI WDT V 2 11 WDO C 3 14 W/T IN POR 17 RT 4 13 WDE 17 SW 3 10 RST SYNC 5 12 FB OUT 6 11 EN/UVLO DA 4 9 WDI BST 7 10 DA 5 6 7 8 V 8 9 SW IN MSE PACKAGE 16-LEAD PLASTIC MSOP = 43C/W, = 4.3C/W JA JC EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB UD PACKAGE 16-LEAD (3mm 3mm) PLASTIC QFN = 68C/W, = 4.2C/W JA JC EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3689EMSE PBF LT3689EMSE TRPBF 3689 16-Lead Plastic MSOP with Exposed Pad 40C to 125C LT3689IMSE PBF LT3689IMSE TRPBF 3689 16-Lead Plastic MSOP with Exposed Pad 40C to 125C LT3689HMSE PBF LT3689HMSE TRPBF 3689 16-Lead Plastic MSOP with Exposed Pad 40C to 150C LT3689EMSE-5 PBF LT3689EMSE-5 TRPBF 36895 16-Lead Plastic MSOP with Exposed Pad 40C to 125C LT3689IMSE-5 PBF LT3689IMSE-5 TRPBF 36895 16-Lead Plastic MSOP with Exposed Pad 40C to 125C LT3689HMSE-5 PBF LT3689HMSE-5 TRPBF 36895 16-Lead Plastic MSOP with Exposed Pad 40C to 150C LT3689EUD PBF LT3689EUD TRPBF LDND 40C to 125C 16-Lead (3mm 3mm) Plastic QFN LT3689IUD PBF LT3689IUD TRPBF LDND 16-Lead (3mm 3mm) Plastic QFN 40C to 125C LT3689EUD-5 PBF LT3689EUD-5 TRPBF LFFM 16-Lead (3mm 3mm) Plastic QFN 40C to 125C LT3689IUD-5 PBF LT3689IUD-5 TRPBF LFFM 16-Lead (3mm 3mm) Plastic QFN 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. 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