LTC3355 - 20V 1A Buck DC/DC with Integrated SCAP Charger and Backup Regulator


  • VIN Voltage Range: 3V to 20V
  • VOUT Voltage Range: 2.7V to 5V
  • 1A Current Mode Buck Main Regulator
  • 5A Boost Backup Regulator Powered from Single Supercapacitor
  • Boost Regulator Operates Down to 0.5V for Maximum Utilization of Supercapacitor Energy
  • Programmable Supercapacitor Charge Current to 1A with Overvoltage Protection
  • Charger Supports Single Cell CC/CV Battery Charging
  • Programmable VIN Current Limit
  • Programmable Boost Current Limit
  • VIN Power Fail Indicator
  • VCAP Power Good Indicator
  • VOUT Power On Reset Output
  • Compact 20-Lead 4mm × 4mm QFN Package

Typical Application

LTC3355 Typical Application
LTC3355 Typical Application


The LTC®3355 is a complete input power interrupt ridethrough DC/DC system. The part charges a supercapacitor while delivering load current to VOUT, and uses energy from the supercapacitor to provide continuous VOUT backup power when VIN power is lost. The LTC3355 contains a nonsynchronous constant frequency current mode monolithic 1A buck switching regulator to provide a 2.7V to 5V regulated output voltage from an input supply of up to 20V.

A 1A programmable CC/CV linear charger charges the supercapacitor from VOUT. When the VIN supply drops below the PFI threshold, the devices’s constant frequency nonsynchronous current mode 5A boost switching regulator delivers power from the supercapacitor to VOUT. A thermal regulation loop maximizes charge current while limiting the die temperature to 110°C. The IC has boost, charger and VIN programmable current limits. The LTC3355 is available in a 20-lead 4mm × 4mm QFN surface mount package.


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

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

Part Number Package Code Temp Package
LTC3355EUF#PBF 4x4 QFN-20 UF E 05-08-1710 Yes
LTC3355EUF#TRPBF 4x4 QFN-20 UF E 05-08-1710 Yes
LTC3355IUF#PBF 4x4 QFN-20 UF I 05-08-1710 Yes
LTC3355IUF#TRPBF 4x4 QFN-20 UF I 05-08-1710 Yes

LTC3355 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
LTC3355EUF#PBF 4x4 QFN-20 E $4.64 $3.25 Yes
LTC3355EUF#TRPBF 4x4 QFN-20 E $3.31 Yes
LTC3355IUF#PBF 4x4 QFN-20 I $5.14 $3.60 Yes
LTC3355IUF#TRPBF 4x4 QFN-20 I $3.66 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
DC2040A LTC3355EUF Demo Board | 12V to 4V/1A Buck Regulator + SCAP Charger & Backup Boost Regulator $150.00
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Click here to view our complete list of demo boards


  • Ride-Through “Dying Gasp” Supplies
  • Power Meters/Industrial Alarms/Solid State Drives

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