Low Power Wireless Charger for Hearing Aids
Features and Benefits
- 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
The LTC4120 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-of-charge 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%.
- Handheld Instruments
- Industrial/Military Sensors and Devices
- Harsh Environments
- Portable Medical Devices
- Physically Small Devices
- Electrically Isolated Devices
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (3)
Demonstration kit DC2386A is a kit of the DC2330A LTC4125EUFD demonstration board, the DC2445A-A/DC2445A-B LTC4120EUD demonstration board, and an assortment of different length standoffs. The DC2330A can deliver up to 1.68W to the receive board with up to 12mm spacing between the transmit and receive coils.
Demonstration circuit 2181A-A features the LTC4120-4.2 wireless power receiver with 400mA synchronous step-down CC/CV (4.2V charge voltage) battery charger. The DC2181 is used with the DC1968A wireless power transmitter or the PowerByProxi ProxiPoint transmitter. Either can deliver 2W to the DC2181, with up to 10mm spacing between the transmitter and the receive coil. The basic transmitter doesn’t support foreign metal object detection.
Demonstration circuit 2181A-B features the LTC4120EUD wireless power receiver with 400mA synchronous step-down CC/CV battery charger. The DC2181 is used with the DC1968A wireless power transmitter or the PowerByProxi ProxiPoint transmitter. Either can deliver 2W to the DC2181, with up to 10mm spacing between the transmitter and the receive coil. The basic transmitter doesn’t support foreign metal object detection.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
Product Selector Card (2)
Solutions Bulletins & Brochures (1)
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Sample & Buy
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 Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.