LTC3128 - 3A Monolithic Buck-Boost Supercapacitor Charger and Balancer with Accurate Input Current Limit


  • ±2% Accurate Average Input Current Limit Programmable Up to 3A
  • Programmable Maximum Capacitor Voltage Limit
  • Active Charge Balancing for Fast Charging of Unmatched Capacitors
  • Charges Single or Stacked Capacitors
  • VIN Range: 1.73V to 5.5V
  • VOUT Range: 1.8V to 5.5V
  • <2μA Quiescent Current from VOUT When Charged
  • Output Disconnect in Shutdown: <1μA IQ Shutdown
  • Power-Good Comparator
  • Power Failure Indicator
  • Thermally Enhanced 20-Lead (4mm × 5mm × 0.75mm) QFN and 24-Lead TSSOP Packages

Typical Application

LTC3128 Typical Application
LTC3128 Typical Application


The LTC®3128 is a highly efficient, buck-boost DC/DC supercapacitor charger. It operates efficiently from input voltages above, below or equal to the output voltage. The LTC3128 incorporates accurate programmable average input current limit, active charge balancing and programmable maximum capacitor voltage. This combination of features makes the LTC3128 ideal for safely charging and protecting large capacitors in backup power systems. The input current limit and maximum capacitor voltage are each programmed using a single resistor. Average input current is accurately controlled over a 0.5A to 3A programmable range while the individual maximum capacitor voltage can be set from 1.8V to 3.0V.

Other features of the LTC3128 include <2μA quiescent current from VOUT in Burst Mode®operation, accurate power-good and power failure indicators, and thermal overload protection. The LTC3128 is offered in low profile, thermally enhanced 20-Lead 4mm × 5mm × 0.75mm QFN and 24-Lead TSSOP packages.


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
LTC3128EFE#PBF TSSOP-24 FE E 05-08-1771 Yes
LTC3128EFE#TRPBF TSSOP-24 FE E 05-08-1771 Yes
LTC3128EUFD#PBF 4x5 QFN-20 UFD E 05-08-1711 Yes
LTC3128EUFD#TRPBF 4x5 QFN-20 UFD E 05-08-1711 Yes
LTC3128IFE#PBF TSSOP-24 FE I 05-08-1771 Yes
LTC3128IFE#TRPBF TSSOP-24 FE I 05-08-1771 Yes
LTC3128IUFD#PBF 4x5 QFN-20 UFD I 05-08-1711 Yes
LTC3128IUFD#TRPBF 4x5 QFN-20 UFD I 05-08-1711 Yes

LTC3128 Package Drawing
LTC3128 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
LTC3128EFE#PBF TSSOP-24 E $6.36 $4.45 Yes
LTC3128EFE#TRPBF TSSOP-24 E $4.51 Yes
LTC3128EUFD#PBF 4x5 QFN-20 E $5.64 $3.95 Yes
LTC3128EUFD#TRPBF 4x5 QFN-20 E $4.01 Yes
LTC3128IFE#PBF TSSOP-24 I $6.93 $4.85 Yes
LTC3128IFE#TRPBF TSSOP-24 I $4.91 Yes
LTC3128IUFD#PBF 4x5 QFN-20 I $6.07 $4.25 Yes
LTC3128IUFD#TRPBF 4x5 QFN-20 I $4.31 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
DC1887A LTC3128 Demo Board | 2-Cell Supercap Charger and Balancer: 1.72Vin to 5.5Vin @up to 3A $150.00
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Click here to view our complete list of demo boards


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  • Industrial, Communications, Computing

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