ZHCSBN3F August 2013 – March 2019
PRODUCTION DATA.
- 1 特性
- 2 应用
- 3 说明
- 4 修订历史记录
- 5 Pin Configuration and Functions
- 6 Specifications
- 7 Detailed Description
- 8 Application and Implementation
- 9 Power Supply Recommendations
- 10Layout
- 11器件和文档支持
- 12机械、封装和可订购信息
7.3.3 Battery Overvoltage Protection
To prevent rechargeable batteries from being exposed to excessive charging voltages and to prevent over charging a capacitive storage element, the overvoltage (VBAT_OV) threshold level must be set using external resistors. This is also the voltage value to which the charger will regulate the VSTOR/VBAT_SEC pin when the input has sufficient power. The VBAT_OV threshold when the battery voltage is rising is given by Equation 2:
The sum of the resistors is recommended to be no higher than 13 MΩ that is, ROV1 + ROV2 = 13 MΩ. Spreadsheet provides help with sizing and selecting the resistors.
The overvoltage threshold when the battery voltage is decreasing is given by VBAT_OV - VBAT_OV_HYST. Once the voltage at the battery reaches the VBAT_OV threshold, the boost converter is disabled. The charger will start again once the battery voltage drop by VBAT_OV_HYST. When there is excessive input energy, the VBAT pin voltage will ripple between the VBAT_OV and the VBAT_OV - VBAT_OV_HYST levels.
CAUTION
If VIN_DC is higher than VSTOR and VSTOR is higher than VBAT_OV, the input VIN_DC is pulled to ground through a small resistance to stop further charging of the attached battery or capacitor. It is critical that if this case is expected, the impedance of the source attached to VIN_DC be higher than 20 Ω and not a low impedance source.