LTC3521 1A Buck-Boost DC/DC and Dual 600mA Buck DC/DC Converters Fea T Descrip T n Three High Efficiency DC/DC Converters: The LTC 3521 combines a 1A buck-boost DC/DC converter Buck-Boost (V : 1.8V to 5.25V, I : 1A) and dual 600mA synchronous buck DC/DC converters. The OUT OUT Dual Buck (V : 0.6V to V , I : 600mA) 1.1MHz switching frequency minimizes the solution foot- OUT IN OUT n 1.8V to 5.5V Input Voltage Range print while maintaining high efficiency. All three converters n Pin-Selectable Burst Mode Operation feature soft-start and internal compensation to minimize n 30A Total Quiescent Current in Burst Mode the solution footprint and simplify the design process. Operation The buck converters are current mode controlled and n Independent Power Good Indicator Outputs utilize an internal synchronous rectifier to improve ef- n Integrated Soft-Start ficiency. The buck converters support 100% duty cycle n Thermal and Overcurrent Protection operation to extend battery life. If the PWM pin is held n <2A Current in Shutdown low, the buck converters automatically transition from n Small 4mm 4mm QFN and Thermally Enhanced Burst Mode operation to PWM mode at high loads. With TSSOP Packages the PWM pin held high, the buck converters remain in low noise, 1.1MHz PWM mode. a T The buck-boost converter features continuous conduction n Bar Code Readers operation to maximize efficiency and minimize noise. At n Medical Instruments light loads, the buck-boost converter can be operated in n Handy Terminals Burst Mode operation to improve efficiency and reduce n PDAs, Handheld PCs no-load standby current. n GPS Receivers The LTC3521 provides a <2A shutdown mode, over- L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks and PowerPath is a trademark of Linear Technology Corporation. All other trademarks are the temperature shutdown and current limit protection property of their respective owners. Protected by U. S. Patents, including 6404251, 6166527. on all converters. The LTC3521 is available in a 24-pin 0.75mm 4mm 4mm QFN package, and a 20-pin ther- mally enhanced TSSOP package. Typical a T Efficiency vs V IN V IN 100 + 2.4V TO 4.2V 4.7F Li-Ion 98 V = 3.3V 4.7H 4.7H PV V PV V OUT1 IN1 IN IN2 OUT2 96 I = 500mA SW1A SW2 1.8V OUT 94 600mA 137k 10F SW1B 92 V OUT1 90 3.3V FB2 V = 1.8V V = 1.2V V OUT3 OUT2 OUT1 88 800mA 68.1k I = 200mA I = 200mA OUT OUT 86 22F (1A, V > 3.0V) 1.0M LTC3521 IN 84 FB1 4.7H V OUT3 82 SW3 1.2V SHDN1 221k ON 80 600mA SHDN2 FB3 OFF 100k 10F 78 SHDN3 PGOOD1 76 PWM PWM PGOOD2 BURST 74 100k PGND1A PGOOD3 72 PGND1B GND PGND2 70 2.4 3.4 4.4 5.4 3521 TA01a V (V) IN 3521 TA01b 3521fb 1 For more information www.linear.com/LTC3521 EFFICIENCY (%) ion pplica ions pplica ion uresLTC3521 a Te Maxi Mu M r a T (Note 1) PV , PV , V Voltage ............................. 0.3V to 6V Voltage, All Other Pins ................................. 0.3V to 6V IN1 IN2 IN SW1A, SW1B, SW2, SW3 Voltage Operating Junction Temperature Range DC ............................................................ 0.3V to 6V (Notes 2, 5) ............................................ 40C to 125C Pulsed < 100ns ............................................1V to 7V Storage Temperature Range .................. 65C to 150C p c F T TOP VIEW TOP VIEW FB3 1 20 PV IN2 FB2 2 19 SW2 24 23 22 21 20 19 SHDN2 3 18 PGND2 SHDN2 1 18 PGND2 PGOOD3 4 17 SW3 PGOOD3 2 17 SW3 PGOOD2 5 16 V 21 OUT1 PGOOD2 V 3 16 25 OUT1 PGND1A PGND1A PGOOD1 6 15 SW1A PGOOD1 4 15 SW1A V 7 14 SW1B V 5 14 SW1B IN IN GND 8 13 PV GND 6 13 NC IN1 PWM 9 12 SHDN1 7 8 9 10 11 12 FB1 10 11 SHDN3 FE PACKAGE 20-LEAD PLASTIC TSSOP UF PACKAGE T = 150C, = 40C/W (NOTE 4) JMAX JA 24-LEAD (4mm 4mm) PLASTIC QFN UNDERSIDE METAL INTERNALLY CONNECTED TO V (PCB CONNECTION OPTIONAL) EXPOSED PAD (PIN 21) IS PGND1A AND MUST BE SOLDERED TO PCB GROUND T = 125C, = 37C/W JMAX JA EXPOSED PAD (PIN 25) IS PGND1A AND MUST BE SOLDERED TO PCB GROUND o r D i n F Ma T LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3521EFE PBF LTC3521EFE TRPBF LTC3521FE 20-Lead Plastic TSSOP 40C to 125C LTC3521IFE PBF LTC3521IFE TRPBF LTC3521FE 20-Lead Plastic TSSOP 40C to 125C LTC3521EUF PBF LTC3521EUF TRPBF 3521 24-Lead (4mm 4mm) Plastic QFN 40C to 125C LTC3521IUF PBF LTC3521IUF TRPBF 3521 24-Lead (4mm 4mm) 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. For more information on lead free part marking, go to: