TI公司的BQ24040是一款应用于面积受限的便携式锂离子和锂聚合物电池线性充电芯片，该芯片的供电部分可以来自于USB供电或AC电源适配器供电，可以使用廉价的未经校准的电源适配器进行供电，因具有高的输入电压供电范围及输入过压保护。电池充电分为三个阶段，条件充电阶段、恒流充电阶段、恒压充电阶段。在所有充电阶段，内部有监测控制回路，当芯片内部温度超过阀值时，通过减少充电电流实现对整体电路的保护。本文首先介绍芯片的简介、特性、内部框图及应用方向，并给出相应设计方案的设计原理图、元器件列表及PCB元件布局图。
The BQ24040 series of devices are highly integrated Li-Ion and Li-Pol linear chargers devices targeted at spacelimited portable applications. The devices operate from either a USB port or AC adapter. The high input voltage range with input overvoltage protection supports low-cost unregulated adapters.
The BQ24040 has a single power output that charges the battery. A system load can be placed in parallel with the battery as long as the average system load does not keep the battery from charging fully during the 10 hour safety timer.
The battery is charged in three phases: conditioning, constant current and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded.

BQ24040主要特性：
• CHARGING
– 1% Charge Voltage Accuracy
– 10% Charge Current Accuracy
– Pin Selectable USB 100mA and 500mA Maximum Input Current Limit
– Programmable Termination and Precharge Threshold, bq24040 and bq24045
– High voltage (4.35V) Chemistry Support with bq24045
• PROTECTION
– 30V Input Rating; with 6.6V or 7.1V Input Overvoltage Protection
– Input Voltage Dynamic Power Management
– 125°C Thermal Regulation; 150°C Thermal Shutdown Protection
– OUT Short-Circuit Protection and ISET short detection
– Operation over JEITA Range via Battery NTC – 1/2 Fast-Charge-Current at Cold, 4.06V at Hot, bq24040 and bq24045
– Fixed 10 Hour Safety Timer, bq24040 and bq24045
• SYSTEM
– Automatic Termination and Timer Disable Mode (TTDM) for Absent Battery Pack With Thermistor, bq24040 and bq24045
– Status Indication – Charging/Done
– Available in Small 2×2mm2 DFN-10 Package
– Integrated Auto Start Function for Production Line Testing, bq24041

BQ24040应用方向：
• Smart Phones
• PDAs
• MP3 Players
• Low-Power Handheld Devices

图1. BQ24040内部方框图

BQ24040方案介绍：
The bq2404x series of devices are highly integrated Li-ion linear charger devices targeted at space-limited portable applications. The devices operate from either a USB port or AC adapter.
The bq2404x has a single power output that charges the battery. A system load can be placed in parallel with the battery as long as the average system load does not keep the battery from charging fully during the 10 hour safety timer.
The battery is charged in three phases: conditioning, constant current, and constant voltage. In all charge phases, an internal control loop monitors the IC junction temperature and reduces the charge current if an internal temperature threshold is exceeded.
The charger power stage and charge current sense functions are fully integrated. The charger function has high-accuracy current and voltage regulation loops, charge status display, and charge termination. The pre-charge current and termination current threshold are programmed via an external resistor on the bq24040 and bq24045. The fast charge current value is also programmable via an external resistor.

BQ24040方案原理图：

图2. BQ24040方案原理图

BQ24040方案材料清单：


PCB元件布局图：