LT3694/LT3694-1 36V, 2.6A Monolithic Buck Regulator With Dual LDO FEATURES DESCRIPTION n Wide Input Range: 4V to 36V The LT 3694/LT3694-1 are monolithic, current mode n Overvoltage Shutdown Protects Circuit Through DC/DC converters with dual, low dropout regulator con- 70V Transients trollers. The switching converter is a step-down converter n 2.6A Output Switching Regulator with Internal capable of generating up to 2.6A at its output. Each regu- Power Switch lator has independent track/soft-start circuits simplifying n Dual, Low Dropout, Linear Regulator Controllers power supply sequencing and interfacing with micro- with Programmable Current Limit controllers and DSPs. n Tracking/Soft-Start Inputs and Power Good Output The switching frequency is set with a single resistor with a Simplify Soft-Start and Supply Sequencing range of 250kHz to 2.5MHz. The high switching frequency n Uses Small Inductors and Ceramic Capacitors permits the use of small inductors and ceramic capacitors n V = 0.75V (Buck and LDOs) OUT(MIN) leading to very small triple output solutions. The constant- n Adjustable 250kHz to 2.5MHz Switching Frequency switching frequency, combined with low impedance ce- n Accurate Enable Threshold Allows User ramic capacitors, results in low, predictable output ripple. Programmable Undervoltage Lockout Protection circuitry senses the current in the power switch n Options for Clock Synchronization (LT3694) or Clock and external Schottky catch diode to protect the LT3694 Output to Enable Synchronization to Other Switching against short-circuit conditions. Frequency foldback and Regulators (LT3694-1) thermal shutdown provide additional protection. n Thermally Enhanced 28-Lead 4mm 5mm QFN and With its wide input voltage range of 4V to 36V, the LT3694 20-Lead TSSOP Packages regulates a broad array of power sources from 4-cell batteries APPLICATIONS and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. The LT3694 can be n Automotive synchronized to an external clock with the SYNC pin while n Industrial the LT3694-1 offers a CLKOUT pin allowing other DC/DC n DSL and Cable Modems converters to synchronize to the LT3694-1 clock. n Distributed Power Regulation L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks n Wall Transformer Regulation of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION V IN Efficiency at V = 3.3V OUT 4.5V TO 36V 4.7F EN/UVLO V BIAS BST IN 100 0.22F f = 800kHz SW 4.7H OUT1 TRK/SS1 SW 3.3V V = 4.5V IN 90 1.7A TRK/SS2 1nF B340A 34k V = 12V IN DA TRK/SS3 FB1 0.1 47F V = 36V LT3694 80 IN 330pF OUT1 LIM2 41.2k 10k V C1 DRV2 OUT2 70 LIM3 OUT1 2.5V 0.1 450mA DRV3 24.9k OUT3 2.2F 60 FB2 1.8V SYNC 450mA 15.4k 2.2F 50 10.7k PGOOD FB3 0 1 2 3 51.1k 11k I (A) RT OUT GND 36941 TA01b f = 800kHz SW 36941 TA01a 36941fb 1 EFFICIENCY (%)LT3694/LT3694-1 ABSOLUTE MAXIMUM RATINGS (Note 1) V , EN/UVLO (Note 6) ............................... 0.3V to 70V Operating Junction Temperature Range (Notes 2 and 5) IN BST ...........................................................................55V LT3694E ............................................. 40C to 125C BST Above SW ..........................................................25V LT3694I .............................................. 40C to 125C PGOOD ......................................................................16V Storage Temperature Range ................... 65C to 150C TRK/SS, V , FB, RT, SYNC Pins ...................................6V Lead Temperature (Soldering, 10 Sec) C BIAS, LIM2, LIM3 Pins ...............................................7V (TSSOP Only) ................................................... 300C PIN CONFIGURATION TOP VIEW TOP VIEW V 1 20 SW IN 28 27 26 25 24 23 EN/UVLO 2 19 DA EN/UVLO 1 22 DA SYNC(CLKOUT) 3 18 BST SYNC (CLKOUT) 2 21 BST PGOOD 4 17 BIAS PGOOD 3 20 BIAS 29 RT 5 16 V RT 4 19 V 21 C1 C1 GND GND TRK/SS1 5 18 FB1 TRK/SS1 6 15 FB1 TRK/SS2 6 17 TRK/SS3 TRK/SS2 7 14 TRK/SS3 FB2 7 16 FB3 FB2 8 13 FB3 8 DRV2 15 DRV3 DRV2 9 12 DRV3 9 10 11 12 13 14 LIM2 10 11 LIM3 FE PACKAGE 20-LEAD PLASTIC TSSOP UFD PACKAGE = 38C/W 28-LEAD (4mm 5mm) PLASTIC QFN JA EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB = 34C/W JA LT3694-1 PINOUT IS SHOWN IN PARENTHESIS EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB LT3694-1 PINOUT IS SHOWN IN PARENTHESIS ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3694EUFD PBF LT3694EUFD TRPBF 3694 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3694IUFD PBF LT3694IUFD TRPBF 3694 40C to 125C 28-Lead (4mm 5mm) Plastic QFN LT3694EFE PBF LT3694EFE TRPBF LT3694FE 20-Lead Plastic TSSOP 40C to 125C LT3694IFE PBF LT3694IFE TRPBF LT3694FE 20-Lead Plastic TSSOP 40C to 125C LT3694-1EUFD PBF LT3694-1EUFD TRPBF 36941 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3694-1IUFD PBF LT3694-1IUFD TRPBF 36941 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3694-1EFE PBF LT3694-1EFE TRPBF LT3694FE-1 20-Lead Plastic TSSOP 40C to 125C LT3694-1IFE PBF LT3694-1IFE TRPBF LT3694FE-1 20-Lead Plastic TSSOP 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: