ST公司的 STEVAL-ISA076V2是基于L6924U的USB兼容的锂电池充电解决方案.L6924U是单片电池充电器,能从USB电源或外接AC适配器对单节锂离子/锂聚合物电池进行充电,支持USB低电压和高电压模式,可编程电流高达1A(AC适配器模式),输出电压4.2V± 1 %,线性或准脉冲工作模式,主要用在PDA,GPS和MP3播放器,USB供电设备,手机,数码相机,无线设备和单独充电器.本文介绍了L6924U主要特性,框图,基本应用电路和演示板STEVAL-ISA076V2主要特性,电路图,材料清单和PCB布局图.
The L6924U is a fully monolithic battery charger that safely charges single-cell Li-Ion/Polymer battery from either an USB power source or an AC adapter. In USB mode, the L6924U supports both low power and high power mode. Alternatively the device can charge from an AC wall adapter. The ideal solution for space-limited portable products integrates the power MOSFET, reverse blocking diode, sense resistor and thermal protection into a compact VFQFPN16 package. When an external voltage regulated adapter or USB port is used, the L6924U works in linear mode, and charges the battery in a constant current constant voltage (CC/CV) profile. Moreover, when a current-limited adapter is used, the device can operate in quasi-pulse mode, dramatically reducing the power dissipation.
Regardless of the charging approach, a closed loop thermal control avoids device overheating. The device has an operating input voltage ranging from 2.5 V to 12 V and it allows the user to program many parameters, such as fast-charge current, end-of-charge current threshold, and charge timer. The L6924U offers two open collector outputs for diagnostic purposes, which can be used to either drive two external LEDs or communicate with a host microcontroller. Finally, the L6924U also provides other features like gas gauge function, check for battery presence, and monitors and protects the battery from unsafe thermal conditions.

L6924U主要特性:
■ Fully integrated solution, with power MOSFET, reverse blocking diode, sense resistor, and thermal protection
■ Charges single-cell Li-Ion batteries from selectable AC adapter or USB input
■ Programmable charge current up to 1 A in AC adapter mode
■ Programmable charging current in USB mode for both high power and low power inputs
■ 4.2 V output voltage with ± 1 % accuracy
■ Linear or quasi-pulse operating mode
■ Closed loop thermal control
■ Programmable end-of-charge current
■ Programmable charge timer
■ (NTC) or (PTC) thermistor interface for battery temperature monitoring and protection
■ Status outputs to drive LEDs or to interface with a host processor
■ Small VFQFPN 16-leads package (3 x 3 mm)

L6924U应用:
■ PDAs, GPS and MP3 players
■ USB powered devices
■ Cellular phones
■ Digital still cameras
■ Standalone chargers
■ Wireless appliances

图1.L6924U框图

图2.L6924U基本应用电路图

演示板STEVAL-ISA076V2
The STEVAL-ISA076V2 demonstration board is based on the L6924U which is a fully monolithic battery charger dedicated to single-cell Li-Ion/Polymer battery packs. It is the ideal solution for space-limited applications, such as PDAs, handheld equipment, cellular phones, and digital cameras.
When an external voltage regulated adapter or USB port is used, the L6924U works in linear mode, and charges the battery in a constant current/constant voltage (CC/CV) profile.
Moreover, when a current-limited adapter is used, the device can operate in Quasi-Pulse Mode, dramatically reducing the power dissipation.

演示板STEVAL-ISA076V2主要特性:
■ Operating input voltage up to 12 V
■ Fully integrated solution with power MOSFET, reverse blocking diode, sense resistor, and thermal control
■ AC adapter or USB mode selection
■ Programmable charge current for both AC adapter and USB power sources separately
■ Low power/high power selection in USB mode
■ Both linear and quasi-pulse operation
■ 4.2 V preset charge voltage (±1 % accuracy)
■ Programmable termination current
■ Programmable charge timer
■ Status outputs to drive LEDs or host processor interface
■ Battery absence detection
■ Closed loop thermal control
■ NTC or PTC thermistor interface for battery temperature monitoring and protection
■ RoHS compliant

图3.演示板STEVAL-ISA076V2外形图

图4.演示板STEVAL-ISA076V2电路图
演示板STEVAL-ISA076V2材料清单(BOM):


图5.演示板STEVAL-ISA076V2 PCB布局图(顶层)

图6.演示板STEVAL-ISA076V2 PCB布局图(底层)