LTC4120/LTC4120-4.2 - Wireless Power Receiver and 400mA Buck Battery Charger


  • Dynamic Harmonization Control Optimizes Wireless Charging Over a Wide Coupling Range
  • Wide Input Voltage Range: 12.5V to 40V
  • Adjustable Float Voltage: 3.5V to 11V
  • Fixed 4.2V Float Voltage Option: LTC4120-4.2
  • 50mA to 400mA Charge Current Programmed with a Single Resistor
  • ±1% Feedback Voltage Accuracy
  • Programmable 5% Accurate Charge Current
  • No Microprocessor Required
  • No Transformer Core
  • Thermally Enhanced, Low Profile 16-Lead (3mm × 3mm × 0.75mm) QFN Package

Typical Application

LTC4120 Typical Application
LTC4120 Typical Application


The LTC®4120 is a constant-current/constant-voltage wireless receiver and battery charger. An external programming resistor sets the charge current up to 400mA. The LTC4120-4.2 is suitable for charging Li-Ion/Polymer batteries, while the programmable float voltage of the LTC4120 accommodates several battery chemistries. The LTC4120 uses a Dynamic Harmonization Control (DHC) technique that allows high efficiency contactless charging across an air gap.

The LTC4120 regulates its input voltage via the DHC pin. This technique modulates the resonant frequency of a receiver tank to automatically adjust the power received as well as the power transmitted to provide an efficient solution for wirelessly charging battery-powered devices.

Wireless charging with the LTC4120 provides a method to power devices in harsh environments without requiring expensive failure-prone connectors. This allows products to be charged while locked within sealed enclosures, or in moving or rotating equipment, or where cleanliness or sanitation is critical.

This full featured battery charger includes accurate RUN pin threshold, low voltage battery preconditioning and bad battery fault detection, timer termination, auto-recharge, and NTC temperature qualified charging. The FAULT pin provides an indication of bad battery or temperature faults.

Once charging is terminated, the LTC4120 signals end-ofcharge via the CHRG pin, and enters a low current sleep mode. An auto-restart feature starts a new charging cycle if the battery voltage drops by 2.2%.


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
LTC4120EUD-4.2#PBF 3x3 QFN-16 UD E 05-08-1691 Yes
LTC4120EUD-4.2#TRPBF 3x3 QFN-16 UD E 05-08-1691 Yes
LTC4120EUD#PBF 3x3 QFN-16 UD E 05-08-1691 Yes
LTC4120EUD#TRPBF 3x3 QFN-16 UD E 05-08-1691 Yes
LTC4120IUD-4.2#PBF 3x3 QFN-16 UD I 05-08-1691 Yes
LTC4120IUD-4.2#TRPBF 3x3 QFN-16 UD I 05-08-1691 Yes
LTC4120IUD#PBF 3x3 QFN-16 UD I 05-08-1691 Yes
LTC4120IUD#TRPBF 3x3 QFN-16 UD I 05-08-1691 Yes

LTC4120 Package Drawing
LTC4120 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
LTC4120EUD-4.2#PBF 3x3 QFN-16 E $4.64 $3.25 Yes
LTC4120EUD-4.2#TRPBF 3x3 QFN-16 E $3.31 Yes
LTC4120EUD#PBF 3x3 QFN-16 E $4.64 $3.25 Yes
LTC4120EUD#TRPBF 3x3 QFN-16 E $3.31 Yes
LTC4120IUD-4.2#PBF 3x3 QFN-16 I $5.36 $3.75 Yes
LTC4120IUD-4.2#TRPBF 3x3 QFN-16 I $3.81 Yes
LTC4120IUD#PBF 3x3 QFN-16 I $5.36 $3.75 Yes
LTC4120IUD#TRPBF 3x3 QFN-16 I $3.81 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
DC2181A-A LTC4120EUD-4.2 Demo Board | Wireless Power Receiver and 400mA Buck Battery Charger with Fixed 4.2V charge voltage and separate receive coil. DC2181A-A requires a transmitter such as DC1969A-B or the Proxi-Point Power-by-Proxi transmitter. $225.00
DC2181A-B LTC4120EUD Demo Board | Wireless Power Receiver and 400mA Buck Battery Charger with Adjustable charge voltage and separate receiver coil. DC2181A-B requires a transmitter such as DC1969A-B or the Proxi-Point Power-by-Proxi transmitter. $225.00
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


  • Handheld Instruments
  • Industrial/Military Sensors and Devices
  • Harsh Environments
  • Portable Medical Devices
  • Physically Small Devices
  • Electrically Isolated Devices

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