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.


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

QFN-20, TSSOP-24

LTC3128 Package Drawing
LTC3128 Package Drawing

Order Info

Package Variations and Pricing

Part Number Package Pins Temp Price (1-99) Price (1k)* RoHS Data
LTC3128EFE#PBF TSSOP 24 E $6.36 $4.45 View
LTC3128EFE#TRPBF TSSOP 24 E $4.51 View
LTC3128EUFD#PBF QFN 20 E $5.64 $3.95 View
LTC3128EUFD#TRPBF QFN 20 E $4.01 View
LTC3128IFE#PBF TSSOP 24 I $6.93 $4.85 View
LTC3128IFE#TRPBF TSSOP 24 I $4.91 View
LTC3128IUFD#PBF QFN 20 I $6.07 $4.25 View
LTC3128IUFD#TRPBF QFN 20 I $4.31 View
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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 Contact Factory
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Click here to view our complete list of demo boards


  • Supercapacitor Based Backup Power
  • Memory Backup
  • Servers, RAID, RF Systems
  • Industrial, Communications, Computing

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