LTC3350IUHF#PBF Analog Devices

LTC3350 High Current Supercapacitor Backup Controller and System Monitor FEATURES DESCRIPTION n High Efficiency Synchronous Step-Down CC/CV The LTC 3350 is a backup power controller that can charge Charging of One to Four Series Supercapacitors and monitor a series stack of one to four supercapacitors. n Step-Up Mode in Backup Provides Greater The LTC3350s synchronous step-down controller drives Utilization of Stored Energy in Supercapacitors N-channel MOSFETs for constant current/constant volt- n 14-Bit ADC for Monitoring System Voltages/ age charging with programmable input current limit. In Currents, Capacitance and ESR addition, the step-down converter can run in reverse as n Active Overvoltage Protection Shunts a step-up converter to deliver power from the superca- n Internal Active BalancersNo Balance Resistors pacitor stack to the backup supply rail. Internal balancers n V : 4.5V to 35V, V : Up to 5V per Capacitor, eliminate the need for external balance resistors and each IN CAP(n) Charge/Backup Current: 10+A capacitor has a shunt regulator for overvoltage protection. n Programmable Input Current Limit Prioritizes System The LTC3350 monitors system voltages, currents, stack Load Over Capacitor Charge Current capacitance and stack ESR which can all be read over n Dual Ideal Diode PowerPath Controller 2 the I C/SMBus. The dual ideal diode controller uses n All N-FET Charger Controller and PowerPath Controller N-channel MOSFETs for low loss power paths from the n Compact 38-Lead 5mm 7mm QFN Package input and supercapacitors to the backup system supply. n AEC-Q100 Qualified for Automotive Applications The LTC3350 is available in a low profile 38-lead 5mm 7mm 0.75mm QFN surface mount package. APPLICATIONS All registered trademarks and trademarks are the property of their respective owners. Patentspending. n High Current 12V Ride-Through UPS n Servers/Mass Storage/High Availability Systems TYPICAL APPLICATION High Current Supercapacitor Charger and Backup Supply I (STEP-DOWN) I CHG BACKUP V V IN OUT Backup Operation INFET VOUTSP VOUTSN P = 25W PFI OUTFB BACKUP V > V CAP OUT V OUT (DIRECT 2V/DIV OUTFET CONNECT) V < V CAP OUT (STEP-UP) TGATE V OUT V CAP 2V/DIV SW V V CAP IN BGATE 2V/DIV LTC3350 V IN ICAP 0V VCAP 2 CAP4 V I C CAP 10F 3350 TA01a 400ms/DIV CAP3 BACK PAGE APPLICATION CIRCUIT 10F CAP2 10F CAP1 10F CAPRTN 3350 TA01a CAPFB Rev. D 1 Document Feedback For more information www.analog.comLTC3350 TABLE OF CONTENTS Features ..................................................... 1 Limit Checking and Alarms .....................................20 Applications ................................................ 1 Die Temperature Sensor .........................................20 Typical Application ........................................ 1 General Purpose Input ............................................20 Description.................................................. 1 Applications Information ................................ 21 Absolute Maximum Ratings .............................. 3 Digital Configuration ...............................................21 Order Information .......................................... 3 Capacitor Configuration ..........................................21 Pin Configuration .......................................... 3 Capacitor Shunt Regulator Programming ...............21 Electrical Characteristics ................................. 4 Setting Input and Charge Currents .........................21 Typical Performance Characteristics ................... 7 Low Current Charging and High Current Backup ....22 Pin Functions .............................................. 10 Setting V Voltage ...............................................22 CAP Block Diagram ............................................. 13 Power-Fail Comparator Input Voltage Threshold ...22 Timing Diagram ........................................... 14 Setting V Voltage in Backup Mode ....................23 OUT Operation................................................... 14 Compensation ......................................................... 24 Introduction ............................................................ 14 Minimum V Voltage in Backup Mode ................. 24 CAP Bidirectional Switching ControllerStep-Down Optimizing Supercapacitor Energy Storage Mode ...................................................................... 14 Capacity ..................................................................25 Bidirectional Switching ControllerStep-Up Capacitor Selection Procedure ...............................26 Mode ...................................................................... 15 Inductor Selection...................................................26 Ideal Diodes ............................................................ 16 C and C Capacitance ....................................27 OUT CAP Gate Drive Supply (DRV ) .................................... 17 Power MOSFET Selection .......................................28 CC Undervoltage Lockout (UVLO) ............................... 17 Schottky Diode Selection ........................................28 RT Oscillator and Switching Frequency .................. 17 Top MOSFET Driver Supply (C , D ) .......................29 B B Input Overvoltage Protection ................................. 17 INTV /DRV and IC Power Dissipation ...............29 CC CC V DAC ............................................................... 17 Minimum On-Time Considerations..........................30 CAP Power-Fail (PF) Comparator.................................... 17 Ideal Diode MOSFET Selection ...............................30 Charge Status Indication......................................... 17 PCB Layout Considerations ....................................30 Capacitor Voltage Balancer .................................... 17 Register Map .............................................. 32 Capacitor Shunt Regulators .................................... 18 Register Descriptions .................................... 33 2 I C/SMBus and SMBALERT .................................... 18 Typical Applications ...................................... 39 Analog-to-Digital Converter .................................... 18 Package Description ..................................... 44 Capacitance and ESR Measurement ...................... 18 Revision History .......................................... 45 Monitor Status Register .......................................... 19 Typical Application ....................................... 46 Charge Status Register ...........................................20 Related Parts .............................................. 46 Rev. D 2 For more information www.analog.com