LTC4125 - 5W AutoResonant Wireless Power Transmitter


  • Monolithic 5W Wireless Power Transmitter
  • AutoResonantTM Switching Frequency Adjusts to Resonant Capacitance and Transmit Coil Inductance*
  • Transmit Power Automatically Adjusts to Receiver Load*
  • Input Voltage Range: 3V to 5.5V
  • Integrated 100mΩ Full Bridge Switches
  • Multiple Foreign Object Detection Methods
  • Programmable Average Input Current Limit and Monitor
  • NTC Input for System/Component Temperature Qualified Power Transfer
  • Wide Operating Switching Frequency Range: 50kHz to 250kHz
  • Thermally Enhanced 4mm × 5mm QFN 20-Lead Package

Typical Application

LTC4125 Typical Application


The LTC®4125 is a simple and high performance monolithic full bridge resonant driver capable of delivering over 5W of power wirelessly to a properly tuned receiver. The device controls the current flow in a series connected transmit coil LC network to create a simple, safe and versatile wireless power transmitter.

The LTC4125 automatically adjusts its driving frequency to match the LC network resonant frequency. This AutoResonant switching allows the device to deliver maximum power from a low voltage input supply (3V to 5.5V) to a tuned receiver. To optimize system efficiency, the LTC4125 employs a periodic transmit power search and adjusts the transmission power based on the receiver load requirements. The device stops delivering power during a fault condition, or if a foreign object is detected.

The LTC4125 also includes a programmable maximum average input current limit and an NTC input as additional means for foreign object and overload protection. The LTC4125 is available in a 20-lead low profile (0.75mm) 4mm × 5mm QFN 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
LTC4125EUFD#PBF 4x5 QFN-20 UFD E 05-08-1711 Yes
LTC4125EUFD#TRPBF 4x5 QFN-20 UFD E 05-08-1711 Yes
LTC4125IUFD#PBF 4x5 QFN-20 UFD I 05-08-1711 Yes
LTC4125IUFD#TRPBF 4x5 QFN-20 UFD I 05-08-1711 Yes

LTC4125 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
LTC4125EUFD#PBF 4x5 QFN-20 E $5.71 $4.00 Yes
LTC4125EUFD#TRPBF 4x5 QFN-20 E $4.06 Yes
LTC4125IUFD#PBF 4x5 QFN-20 I $6.29 $4.40 Yes
LTC4125IUFD#TRPBF 4x5 QFN-20 I $4.46 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
DC2386A-B Wireless Power Transfer Demonstration Kit featuring the LTC4125EUFD and the LTC4120EUD $150.00
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Click here to view our complete list of demo boards


  • Hermetically and/or Electrically Insulated Devices
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Linear Technology provides a variety of custom design simulation tools and device models to allow even novice designers to quickly and easily evaluate circuits using high performance switching regulators, amplifiers, data converters, filters and more. Please visit our Design Tools page to view and download:

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