Linear公司的LTC4120是无线电源接收器和 400mA 降压型电池充电器,具有动态协调控制可优化宽耦合范围内的无线充电,宽输入电压从4.3V 至 40V,可调电池浮动电压从3.5V 至 11V,采用单个电阻器设置的 50mA 至 400mA 充电电流, ±1%反馈电压准确度, 准确度为 5% 的可编程充电电流,以及无需微处理器和无变压器磁芯等特性,主要用在手持仪表,工业/军用传感器,手持医疗设备以及电隔离设备.本文介绍了LTC4120主要特性,框图,典型应用电路以及演示板DC1969A主要特性,电路图和材料清单.
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 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 2.5%.

LTC4120主要特性:
 Dynamic Harmonization Control Optimizes Wireless Charging Over a Wide Coupling Range
 Wide Input Voltage Range: 4.3V to 40V
 Adjustable Battery Float Voltage: 3.5V to 11V
 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

LTC4120应用:
 Handheld Instruments
 Industrial/Military Sensors and Devices
 Harsh Environments
 Portable Medical Devices
 Physically Small Devices
 Electrically Isolated Devices


图1.LTC 4120框图

图2.LTC 4120典型应用电路

演示板DC1969A
Demonstration circuit DC1969A is a kit of: the DC1967A-X LTC®4120EUD demonstration board, the DC1968A basic wireless transmitter, a 35mm receiver ferrite disk, and an assortment of different length standoffs. The basic transmitter can deliver 2W to the receive board with up to 10mm spacing between the transmit and the receive coils. The basic transmitter does not support foreign object detection, i.e. coins or other metallic objects.

演示板DC1969A套件包括:
 1X DC1967A-X* (LTC4120EUD) Demo Board
 1X DC1968A (Wireless Basic Transmitter) Demo Board
 1X 35mm Ferrite Bead
 4X 6.25mm (0.25") Nylon Standoffs
 4X 12.5mm (0.50") Nylon Standoffs
 4X 15.875mm (0.625") Nylon Standoffs


图3.DC1967A-B LTC4120接收板外形图

图4.DC1968A Basic发送板外形图

图5.无线充电系统功能框图

图6.LTC4120发送器电路图

图7.DC1967A电路图(1)

图8.DC1967A电路图(2)

图9.DC1968A电路图
演示板DC1969A材料清单: