LTC3351 Datasheet

• Integrated Hot Swap Controller with Circuit Breaker
• 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
• 16-Bit ADC for Monitoring System Voltages/Currents, Capacitance and ESR
• Programmable Undervoltage and Overvoltage Thresholds to 35V
• V_IN: 4.5V to 35V, V_CAP(n): Up to 5V per Capacitor, Charge/Backup Current: >10A
• Programmable Input Current Limit Prioritizes System Load Over Capacitor Charge Current
• All N-FET Charger Controller and PowerPath^™ Controller
• Compact 44-Lead 4mm × 7mm QFN Package

• Swappable PCIE Cards with NVM
• High Current 12V Ride-Through UPS
• Servers/Mass Storage/High Availability Systems

The LTC3351 is a backup power controller that charges and monitors a series stack of one to four supercapacitors. The LTC3351’s synchronous step-down controller drives N-channel MOSFETs for constant current/constant voltage charging with programmable input current limit. In addition, the step-down converter runs in reverse as a step-up converter to deliver power from the supercapacitor stack to the backup supply rail. Internal balancers eliminate the need for external balance resistors and each capacitor has a shunt regulator for overvoltage protection.

The LTC3351 monitors system voltages, currents, stack capacitance and ESR which can all be read over the I²C/SMBus port. The hot swap controller uses N-channel MOSFETs for inrush control and a low loss path from the input to the output. The ideal diode controller uses an N-channel MOSFET for a low loss power path from the supercapacitors to the output. The LTC3351 is available in a thermally enhanced low profile 44-lead 4mm × 7mm × 0.75mm QFN surface mount package.