LT3507A Triple Monolithic Step-Down Regulator with LDO Features Description n Wide Input Range: 4V to 36V The LT 3507A is a triple, current mode, DC/DC converter n One 2.7A and Two 1.8A Output Switching with internal power switches and a low dropout regulator. Regulators with Internal Power Switches The switching converters are step-down converters capable n Low Dropout Linear Regulator with External of generating one 2.7A output and two 1.8A outputs. All Transistor three converters are synchronized to a single oscillator. n Antiphase Switching Reduces Ripple The 2.7A output runs with opposite phase to the other two n Independent Run, Tracking/Soft-Start, and Power converters, reducing input ripple current. Each regulator Good Indicators Ease Supply Sequencing has independent shutdown and soft-start circuits, and n Uses Small Inductors and Ceramic Capacitors generates a power good signal when its output is in regu- n Adjustable, 250kHz to 2.5MHz Switching Frequency, lation, easing power supply sequencing and interfacing Synchronizable Over the Full Range with microcontrollers and DSPs. n User Programmable Overvoltage and Undervoltage The switching frequency is set with a single resistor yielding Lockouts a range of 250kHz to 2.5MHz. The high switching frequency n Thermally Enhanced, 38-Lead TSSOP and allows the use of small inductors and capacitors resulting 5mm 7mm QFN Packages in a very small triple output supply. The constant switching frequency, combined with low impedance ceramic capaci- a tors, results in low, predictable output ripple. Frequency n Automotive foldback and thermal shutdown provide protection against n Industrial Supplies fault conditions. The LT3507A provides higher output cur- n Distributed Power Regulation rent than available with the LT3507. n DSP Power L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. t ypical a 5V, 3.3V, 2.5V and 1.8V Step-Down Regulator V IN 6V TO 36V 22F V V V IN1 IN2 IN3 BOOST1 BOOST2 Start-Up WaveformsCoincident Tracking 4.7H 0.22F V OUT1 1.8V SW1 0.22F 2.7A 18.7k 10H V OUT2 100F FB1 SW2 3.3V V OUT3 1.5A 33F 680pF 15k 25.5k V C1 V 34.8k LT3507A OUT2 1V/DIV V OUT2 FB2 V OUT4 BOOST3 0.22F V 15H OUT3 V OUT1 11k 5V 680pF 25.5k SW3 1.8A V C2 53.6k 22F FB3 BIAS 3507 TA01b 680pF 10.2k 1ms/DIV 25.5k DRIVE V C3 V 24.3k OUT4 2.5V FB4 RT/SYNC 0.3A 107k GND 11.5k 2.2F f = 450kHz SW 3507A TA01a 3507afa 1 For more information www.linear.com/LT3507A pplication pplicationsLT3507A a bsolute Maxi Mu M r (Note 1) V Pins ...................................................... 0.3V to 36V DRIVE Pin ...................................................................5V IN BOOST Pins ..............................................................55V Operating Junction Temperature Range (Notes 2, 5) BOOST Above SW .....................................................25V LT3507AE, LT3507AI ......................... 40C to 125C PGOOD Pins ..............................................................36V LT3507AH .......................................... 40C to 150C BIAS Pin ....................................................................16V Storage Temperature Range .................. 65C to 150C TRK/SS, V , FB, RT/SYNC Pins ...................................6V Lead Temperature (Soldering, 10 sec) C RUN, OVLO, UVLO Pins ........................................... V TSSOP Only ......................................................300C IN1 p in c F TOP VIEW TOP VIEW 1 SW3 V 38 IN3 2 BOOST3 SW1 37 3 V SW1 36 IN2 38 37 36 35 34 33 32 4 35 V BOOST1 IN2 BOOST1 1 31 V IN2 5 34 NC V IN1 V 2 30 V IN1 IN2 6 33 SW2 V IN1 V 3 29 SW2 IN1 7 32 BOOST2 V INSW V 4 28 SW2 INSW 8 31 TRK/SS4 OVLO OVLO 5 27 BOOST2 9 30 FB4 UVLO UVLO TRK/SS4 6 26 39 10 39 29 DRIVE V GND C1 V 7 25 FB4 C1 GND 11 28 V TRK/SS1 C2 TRK/SS1 8 24 DRIVE 12 27 NC FB1 FB1 9 23 V C2 13 26 FB2 PGOOD1 10 22 FB2 PGOOD1 PGOOD2 11 21 TRK/SS2 14 25 TRK/SS2 PGOOD2 20 PGOOD3 12 FB3 15 24 FB3 PGOOD3 13 14 15 16 17 18 19 16 23 V RT/SYNC C3 17 22 TRK/SS3 RUN1 18 21 BIAS RUN2 19 20 GND RUN3 UHF PACKAGE 38-LEAD (5mm 7mm) PLASTIC QFN FE PACKAGE = 34C/W JA 38-LEAD PLASTIC TSSOP EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB = 24C/W JA EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB 3507afa 2 For more information www.linear.com/LT3507A RT/SYNC SW1 RUN1 SW1 V RUN2 IN3 RUN3 V IN3 BIAS SW3 TRK/SS3 SW3 V BOOST3 C3 iguration on atings