LT3501 Monolithic Dual Tracking 3A Step-Down Switching Regulator Fea T Descrip T n Wide Input Range: 3.1V to 25V The LT 3501 is a dual-current mode PWM step-down n Two Switching Regulators with 3A Output Capability DC/DC converter with two internal 3.5A switches. Inde- n Independent Supply to Each Regulator pendent input voltage, feedback, soft-start and power n Adjustable/Synchronizable Fixed Frequency good pins for each channel simplify complex power Operation from 250kHz to 1.5MHz supply tracking/sequencing requirements. n Antiphase Switching Both converters are synchronized to either a common n Outputs Can be Paralleled external clock input or a resistor programmable fixed n Independent, Sequential, Ratiometric or Absolute 250kHz to 1.5MHz internal oscillator. At all frequencies, a Tracking Between Outputs 180 phase relationship between channels is maintained, n Independent Soft-Start and Power Good Pins reducing voltage ripple and component size. Programmable n Enhanced Short-Circuit Protection frequency allows for optimization between efficiency and n Low Dropout: 95% Maximum Duty Cycle external component size. n Low Shutdown Current: <10A n Minimum input-to-output voltage ratios are improved 20-Lead TSSOP Package with Exposed Leadframe by allowing the switch to stay on through multiple clock a T cycles, only switching off when the boost capacitor needs recharging, resulting in ~95% maximum duty cycle. n DSP Power Supplies n Disc Drives Each output can be independently disabled using its own n DSL/Cable Modems soft-start pin, or by using the SHDN pin the entire part can n Wall Transformer Regulation be placed in a low quiescent current shutdown mode. n Distributed Power Regulation The LT3501 is available in a 20-lead TSSOP package with L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks exposed leadframe for low thermal resistance. and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Typical a T 3.3V and 1.8V Dual 3A Step-Down Converter with Output Tracking Efficiency V , 12V IN 100 V = 3.3V OUT1 V = 5V OUT1 4.7F 90 V V IN1 IN2 61.9k 80 SHDN R /SYNC T 70 V = 1.8V OUT1 V = 2.5V OUT1 BST1 BST2 4.7H 3.3H 60 0.47F 0.47F SW1 SW2 50 PMEG4005 PMEG4005 B360A B360A 40 LT3501 V 30 OUT2 IND1 IND2 1.8V, 3A V V 20 OUT1 OUT2 V = 12V IN V OUT1 100F I = 0A 10k 24.9k OUT2 3.3V, 3A 10 PG1 PG2 FREQUENCY = 500kHz 47F FB1 FB2 0 0 0.5 1 1.5 2 2.5 3 V V C1 C2 LOAD CURRENT (A) 470pF SS/TRACK1 SS/TRACK2 470pF 8.06k 8.06k 3501 TA01b GND 40.2k 10pF 40.2k 47pF 0.1F 3501 TA01a 3501fd 1 EFFICIENCY (%) ion pplica ions pplica ion uresLT3501 a Te Maxi Mu M r a T p in c F T (Note 1) TOP VIEW V , SHDN, PG1/2 ...................................... 25V/0.3V IN1/2 V 1 20 BST1 SW1/2 ....................................................................V IN1 IN1/2 SW1 2 19 SS/TRACK1 BST1/2 ........................................................... 35V/0.3V IND1 3 18 V C1 BST1/2 Pins Above SW1/2 ........................................25V V 4 17 FB1 OUT1 IND1/2 ......................................................................5A PG1 5 16 R /SYNC T V ........................................................ V /0.3V 21 OUT1/2 IN1/2 PG2 6 15 SHDN FB1/2, SS1/2, R /SYNC ............................................5.5V T V 7 14 FB2 OUT2 V ...................................................................... 1mA C1/2 IND2 8 13 V C2 Operating Junction Temperature Range SW2 9 12 SS/TRACK2 LT3501EFE (Notes 2, 8) ..................... 40C to 125C V 10 11 BST2 IN2 LT3501IFE (Notes 2, 8) ...................... 40C to 125C FE PACKAGE Storage Temperature Range .................. 65C to 150C 20-LEAD PLASTIC TSSOP T = 125C, = 45C/W, = 10C/W JMAX JA JC(PAD) Lead Temperature (Soldering, 10 sec) ...................300C EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB o r Der i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3501EFE PBF LT3501EFE TRPBF LT3501 20-Lead Plastic TSSOP 40C to 125C LT3501IFE PBF LT3501IFE TRPBF LT3501 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: