LTC3351 - Hot Swappable Supercapacitor Charger, Backup Controller and System Monitor


  • 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
  • VIN: 4.5V to 35V, VCAP(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 x 7mm QFN Package

Typical Application

LTC3351 Typical Application
LTC3351 Typical Application


The LTC®3351 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 x 7mm x 0.75mm QFN surface mount package.


For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LTC3351EUFF#PBF 4x7 QFN-44 UFF E 05-08-1500 Yes
LTC3351EUFF#TRPBF 4x7 QFN-44 UFF E 05-08-1500 Yes
LTC3351IUFF#PBF 4x7 QFN-44 UFF I 05-08-1500 Yes
LTC3351IUFF#TRPBF 4x7 QFN-44 UFF I 05-08-1500 Yes

LTC3351 Package Drawing
LTC3351 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LTC3351EUFF#PBF 4x7 QFN-44 E $7.50 $5.25 Yes
LTC3351EUFF#TRPBF 4x7 QFN-44 E $7.56 $5.31 Yes
LTC3351IUFF#PBF 4x7 QFN-44 I $8.29 $5.80 Yes
LTC3351IUFF#TRPBF 4x7 QFN-44 I $8.35 $5.86 Yes
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC2464A-B LTC3351EUFF Demo Board | Hot Swappable Supercapacitor Charger, Backup Controller and System Monitor (24V nominal input, 18V 36W backup) Contact Factory
DC2464A-A LTC3351EUFF Demo Board | Hot Swappable Supercapacitor Charger, Backup Controller and System Monitor (12V nominal input, 6V 25W backup) Contact Factory
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Click here to view our complete list of demo boards


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