Linear Technology Corporation LTC3350: High Current Supercapacitor Backup Controller & System Monitor Tony Armstrong Director of Product Marketing Power Products April, 2014

LTC3350: The Problem It Solves Basic Problem: Many apps need a few seconds of backup time… Capacitors provide simple, reliable and inexpensive short-term backup energy. Monitoring capacitor “state of health” important for two reasons: Ensure adequate energy and power handling for proper backup Extend capacitor lifetime by minimizing capacitor charge voltage What Basic Circuit Building Blocks Are Required to Accomplish This? High power charger for quickly charging backup capacitor stack High power backup dc/dc for providing regulated backup supply Power path control, VIN / VCAP monitor Capacitor balancer and overvoltage protection Capacitor health monitor (stack capacitance and stack ESR measurement system) 2

Supercapacitor Lifetime Characteristics Supercap “end of life” = 30% drop in capacitance or 100% increase in ESR Supercap lifetime degrades faster at high temps 3

Supercapacitor Lifetime Degrades at High Temps Backup Energy (Joules required) = Backup Power*Backup Time Measuring stack capacitance and VCAP  Joules available VCAP can be reduced if Joules available >> Joules required Reducing VCAP increases Cap lifetime ! 4

LTC3350: High Current Supercapacitor Backup Controller and System Monitor: few helpful equations…

LTC3350: What is it? High Current Supercapacitor Backup Controller and System Monitor

LTC3350 Supercap Charger, Backup Controller and SCAP Health Monitor Why did we develop this part? Provide high current cap charging and balancing for 12V systems Provide integrated cap health and system monitoring Provide seamless power path control Provide high efficiency bi-directional power flow to make optimum use of available input power and CAP stored energy Who might use it? Servers, data storage systems Data backup supplies High Capacity Solid State Drives 7

LTC3350 Key Features 4.5V - 40V input / output range High current sync buck charging of 1-4 supercapacitors High current sync boost backup mode for max capacitor energy use Automatic cell balancing, OV shunts and power-path control Internal 14-bit ADC for accurate cap health and system monitoring Measure capacitance Measure capacitor ESR Measure VIN, IIN, VCAP, ICAP I2C interface for data monitoring and capacitor charge control (VCAP adjust) All N-FET design 8

LTC3350 Power Path Control Normal Mode VOUT = VIN CAPS charged from VOUT 9

LTC3350 Power Path Control Backup Mode VOUT = VCAP VCAP > 5V Set min VOUT VOUT = VCAP VCAP > 5V Linear Discharge 10

LTC3350 Power Path Control Backup Mode VOUT = 5V VCAP < 5V Set min VOUT VOUT = 5V VCAP < 5V Boost Mode 11

LTC3350 Typical Backup Operation 12

LTC3350: Block Diagram 13

LTC3350: QFN Package

LTC3350 Typ App: SCAP Charger + Backup 12V, 5A Supercapacitor Charger with 2A Input Current Limit and 6V, 25W Backup Mode 15

LTC3350: Demo Board Active area: X = 4.1cm Y = 2.6cm 16

LTC3350: Summary High Efficiency Synchronous Step-Down CC/CV Charging of One to Four Series Supercapacitors Step-Up Mode in Backup Provides Greater Utilization of Stored Energy in Supercapacitors 14-Bit ADC for Monitoring System Voltages/Currents, Capacitance and ESR Active Overvoltage Protection Shunts Internal Active Balancers - No Balance Resistors VIN: 4.5V to 35V, VCAP(n): Up to 5V per Capacitor, Charge/Backup Current: 10+A Programmable Input Current Limit Prioritizes System Load Over Capacitor Charge Current Dual Ideal Diode PowerPath™ Controller All N-FET Charger Controller and PowerPath Controller Compact 38-Lead 5mm × 7mm QFN Package