LTC3371 4-Channel 8A Configurable Buck DC/DCs with Watchdog and Power-On Reset FEATURES DESCRIPTION n 8 1A Buck Power Stages Configurable as 2, 3 or 4 The LTC 3371 is a highly flexible multioutput power supply Output Channels IC. The device includes four synchronous buck convert- n 8 Unique Output Configurations (1A to 4A Per Channel) ers, configured to share eight 1A power stages, each of n Independent V Supplies for Each DC/DC (2.25V to 5.5V) which is powered from independent 2.25V to 5.5V inputs. IN n Low Total No Load Supply Current: The DC/DCs are assigned to one of eight possible power n 15A In Shutdown (All Channels Off) configurations via pin programmable C1-C3 pins. The n 68A One Channel Active in Burst Mode Operation common buck switching frequency may be programmed n 18A Per Additional Channel with an external resistor, synchronized to an external oscil- n Precision Enable Pin Thresholds for Autonomous lator, or set to a default internal 2MHz clock. The operating Sequencing mode for all DC/DCs may be programmed for Burst Mode n 1MHz to 3MHz RT Programmable Frequency or forced continuous mode operation. (2MHz Default) or PLL Synchronization n The CT pin programs the timing parameters of four inde- Temp Monitor Indicates Die Temperature n pendent RST pins as well as the watchdog timer. CT Programmed Watchdog Timer n Independent RST Pins Indicate Buck in Regulation To reduce input noise, the buck converters are phased in n Thermally Enhanced 38-Lead 5mm 7mm QFN and 90 steps. Precision enable pin thresholds facilitate reli- TSSOP Packages able power sequencing. The LTC3371 is available in low profile 38-lead 5mm 7mm QFN and TSSOP packages. APPLICATIONS 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 n General Purpose Multichannel Power Supplies: owners. Automotive, Industrial, Distributed Power Systems Buck Efficiency vs I TYPICAL APPLICATION LOAD 100 90 80 2.7V TO 5.5V 70 V CC 2.25V TO 5.5V V V 2.25V TO 5.5V INA INE 60 V V 2.2H INB INF 50 V = 1.2V/2A SWA SWE V = 1.8V/2A OUT1 OUT3 SWB SWF 40 324k 806k 30 Burst Mode OPERATION FB1 FB3 V = 3.3V 1A BUCK EN1 EN3 IN 645k 649k 20 RST1 RST3 V = 1.8V 2A BUCK OUT LTC3371 f = 1MHz 10 OSC 3A BUCK L = 3.3H 4A BUCK 2.25V TO 5.5V V V 2.5V TO 5.5V INC ING 0 V V 1 10 100 1000 4000 2.2H IND INH V = 1.5V/2A V = 2.5V/2A LOAD CURRENT (mA) OUT2 SWC SWG OUT4 3371 TA01b SWD SWH 412k 665k FB2 FB4 C3 C2 C1 BUCK1 BUCK2 BUCK3 BUCK4 EN2 EN4 475k 309k RST2 RST4 0 0 0 2A 2A 2A 2A 0 0 1 3A 1A 2A 2A PLL/MODE TEMP RT WDI 0 1 0 3A 1A 1A 3A WDO CT 0 1 1 4A 1A 1A 2A C1 C2 C3 GND 3371 TA01 1 0 0 3A 2A 3A 1 0 1 4A 2A 2A 1 1 0 4A 1A 3A 1 1 1 4A 4A 3371fb 1 For more information www.linear.com/LTC3371 EFFICIENCY (%)LTC3371 TABLE OF CONTENTS Features ..................................................... 1 Applications Information ................................ 18 Applications ................................................ 1 Buck Switching Regulator Output Voltage and Typical Application ........................................ 1 Feedback Network .................................................. 18 Description.................................................. 1 Buck Regulators ..................................................... 18 Absolute Maximum Ratings .............................. 3 Combined Buck Power Stages ................................ 18 Pin Configuration .......................................... 3 Input and Output Decoupling Capacitor Selection... 18 Order Information .......................................... 3 PCB Considerations ................................................20 Electrical Characteristics ................................. 4 Typical Applications ...................................... 20 Typical Performance Characteristics ................... 6 Package Description ..................................... 23 Pin Functions .............................................. 12 Revision History .......................................... 25 Block Diagram ............................................. 14 Typical Application ....................................... 26 Operation................................................... 15 Related Parts .............................................. 26 Buck Switching Regulators ..................................... 15 Buck Regulators with Combined Power Stages ...... 15 Power Failure Reporting Via RST Pins .................... 16 Temperature Monitoring and Overtemperature Protection ............................................................... 16 Programming the Operating Frequency .................. 16 Windowed Watchdog Timer .................................... 17 Choosing the C Capacitor ...................................... 17 T 3371fb 2 For more information www.linear.com/LTC3371