LTC3125 - 1.2A Synchronous Step-Up DC/DC Converter with Input Current Limit


  • Programmable Average Input Current Limit
  • 5% Input Current Accuracy
  • 200mA to 1000mA Program Range
  • VIN: 1.8V to 5.5V, VOUT: 2V to 5.25V
  • Supports High Current GSM/GPRS Load Burst
  • VIN > VOUT Operation
  • 1.6MHz Fixed Frequency Operation
  • Internal Current Sense Resistor
  • 1.2A Peak Current Limit
  • Up to 93% Efficiency
  • Output Disconnect in Shutdown
  • Soft-Start
  • Low Quiescent Current Burst Mode® Operation (15μA)
  • Available in 2mm × 3mm × 0.75mm DFN Package

Typical Application

LTC3125 Typical Application
LTC3125 Typical Application


The LTC3125 is a high efficiency, synchronous step-up DC/DC converter with an accurate programmable average input current limit. The resistor programmable average input current limit is 5% accurate at 500mA and is suitable for a wide variety of applications. In mobile computing, GSM and GPRS cards demand high current pulses well beyond the capability of the PC Card and CompactFlash slots. The LTC3125 in concert with a reservoir capacitor, keeps the slot power safely within its capabilities providing a high performance and simple solution.

Synchronous rectification produces high efficiency while the 1.6MHz switching frequency minimizes the solution footprint. The current mode PWM design is internally compensated. Output disconnect allows the load to discharge in shutdown, while also providing inrush current limiting.

Other features include a <1μA shutdown current, short circuit and thermal overload protection. The LTC3125 is offered in a low profile 0.75mm × 2mm × 3mm 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
LTC3125EDCB#PBF 2x3 DFN-8 DCB E 05-08-1718 Yes
LTC3125EDCB#TRMPBF 2x3 DFN-8 DCB E 05-08-1718 Yes
LTC3125EDCB#TRPBF 2x3 DFN-8 DCB E 05-08-1718 Yes

LTC3125 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
LTC3125EDCB#PBF 2x3 DFN-8 E $3.22 Yes
LTC3125EDCB#TRMPBF 2x3 DFN-8 E $3.22 $2.30 Yes
LTC3125EDCB#TRPBF 2x3 DFN-8 E $3.22 $2.25 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
DC1267A LTC3125EDCB Demo Board | 1.5A Switch, 3.3V Input, Vout = 4V @ 500mA (2A Pulses) $150.00
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Click here to view our complete list of demo boards


  • GSM/GPRS PCMCIA/CompactFlash PC Card Modems
  • Wireless Emergency Locators
  • Portable Radios
  • Supercap Chargers

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Design Tools


LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

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