Features

• 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

Description

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%.