LT3508 Dual Monolithic 1.4A Step-Down Switching Regulator FEATURES DESCRIPTION n Wide Input Voltage Range: 3.7V to 36V The LT 3508 is a dual current mode PWM step-down n Two 1.4A Output Switching Regulators with Internal DC/DC converter with internal power switches capable Power Switches of generating two 1.4A outputs. The wide input voltage n Adjustable 250kHz to 2.5MHz Switching Frequency range of 3.7V to 36V makes the LT3508 suitable for reg- n Synchronizable over the Full Frequency Range ulating power from a wide variety of sources, including n Anti-Phase Switching Reduces Ripple automotive batteries, 24V industrial supplies and unreg- n Uses Small Inductors and Ceramic Capacitors ulated wall adapters. Both converters are synchronized n Accurate Programmable Undervoltage Lockout to a single oscillator programmable up to 2.5MHz and n Independent Tracking, Soft-Start and Power Good run with opposite phases, reducing input ripple current. Circuits Ease Supply Sequencing Its high operating frequency allows the use of small, low n Output Adjustable Down to 800mV cost inductors and ceramic capacitors, resulting in low, n Small 4mm 4mm 24-Pin QFN or 16-Pin Thermally predictable output ripple. Each regulator has independent Enhanced TSSOP Surface Mount Packages tracking and soft-start circuits and generates a power n AEC-Q100 Qualified for Automotive Applications good signal when its output is in regulation, easing power supply sequencing and interfacing with microcontrollers and DSPs. APPLICATIONS Cycle-by-cycle current limit, frequency foldback and ther- n Automotive mal shutdown provide protection against shorted out- n DSP Power Supplies puts, and soft-start eliminates input current surge during n Wall Transformer Regulation start-up. The low current (<2A) shutdown mode enables n DSL and Cable Modems easy power management in battery-powered systems. n PCI Express All registered trademarks and trademarks are the property of their respective owners. TYPICAL APPLICATION 3.3V and 5V Dual Output Step-Down Converter with Output Sequencing Efficiency V IN ON OFF 5.6V TO 36V 95 4.7F V = 12V IN V V IN1 IN2 SHDN OUT2 V = 5V OUT2 90 BOOST1 BOOST2 5V 1.4A 0.22F 0.22F 6.8H OUT1 10H V = 3.3V OUT1 85 3.3V SW1 SW2 1.4A LT3508 80 35.7k 56.2k FB1 FB2 75 V V C1 C2 11.5k 51k TRACK/SS1 PG1 43k 10.7k 10F 70 TRACK/SS2 PG2 100k 22F 150pF GND RT/SYNC 65 0 0.5 1 1.5 100pF 1nF 52.3k LOAD CURRENT (A) 3508 TA01b POWER f = 700kHz SW 3508 TA01a GOOD Rev. E 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LT3508 ABSOLUTE MAXIMUM RATINGS (Notes 1, 7) V Pin Voltage ............................................(0.3V), 40V LT3508H ............................................ 40C to 150C IN BOOST Pin Voltage ...................................................60V Storage Temperature Range BOOST Above SW Voltage ........................................30V QFN .................................................... 65C to 150C SHDN, PG Voltage ....................................................40V TSSOP ............................................... 65C to 150C TRACK/SS, FB, RT/SYNC, V Voltage .........................6V Lead Temperature (Soldering, 10 sec) C Operating Junction Temperature Range (Note 2) TSSOP ..............................................................300C LT3508E ............................................ 40C to 125C LT3508I ............................................. 40C to 125C PIN CONFIGURATION TOP VIEW TOP VIEW TRACK/SS1 1 16 FB1 24 23 22 21 20 19 BOOST1 2 15 V C1 FB1 1 18 FB2 SW1 3 14 PG1 TRACK/SS1 2 17 TRACK/SS2 V 4 13 RT/SYNC IN1 17 GND 3 16 GND 25 GND V 5 12 SHDN GND IN2 GND 4 15 GND SW2 6 PG2 11 GND 5 14 GND 7 6 13 GND BOOST2 10 V GND C2 TRACK/SS2 8 9 FB2 7 8 9 10 11 12 FE PACKAGE 16-LEAD PLASTIC TSSOP UF PACKAGE = 40C/W, = 10C/W JA JC 24-LEAD (4mm 4mm) PLASTIC QFN EXPOSED PAD (PIN 17) IS GND AND MUST BE SOLDERED TO PCB = 40C/W, = 10C/W JA JC EXPOSED PAD (PIN 25) IS GND AND MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3508EFE PBF LT3508EFE TRPBF 3508FE 16-Lead Plastic TSSOP 40C to 125C LT3508IFE PBF LT3508IFE TRPBF 3508FE 16-Lead Plastic TSSOP 40C to 125C LT3508HFE PBF LT3508HFE TRPBF 3508HFE 16-Lead Plastic TSSOP 40C to 150C LT3508EUF PBF LT3508EUF TRPBF 3508 24-Lead (4mm 4mm) Plastic QFN 40C to 125C LT3508IUF PBF LT3508IUF TRPBF 3508 24-Lead (4mm 4mm) Plastic QFN 40C to 125C LT3508HUF PBF LT3508HUF TRPBF 3508H 24-Lead (4mm 4mm) Plastic QFN 40C to 150C AUTOMOTIVE PRODUCTS** LT3508IFE WPBF LT3508IFE WTRPBF 3508FE 16-Lead Plastic TSSOP 40C to 125C LT3508HFE WPBF LT3508HFE WTRPBF 3508HFE 16-Lead Plastic TSSOP 40C to 150C Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with TRMPBF suffix. **Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These models are designated with a W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for thesemodels. Rev. E 2 For more information www.analog.com BOOST1 V C1 SW1 PG1 V RT/SYNC IN1 V SHDN IN2 SW2 PG2 BOOST2 V C2