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BQ76952: 技术咨询

Part Number: BQ76952

你好,  

    在调试BQ76952 出现如下问题, 请帮忙协助解答一下,谢谢!, 

1、单体电压刷新慢,延迟好几秒;
2、MOS驱动能力弱;
3、单体硬件过压解除后,充电MOS不自动恢复;
4、单体硬件欠压后,放电MOS不自动关闭;
5、预放电MOS驱动无信号输出;

  • 您好,请将电路和参数文件发过来看一下。

  • 请参考电路:

                                         

    上电后执行 BQ769x2_Init 函数初始化芯片

    每500ms执行一次 BQ769x2_SampCurr 函数,在改函数内调用 MosCtrolTest 进行MOS驱动信号测试

    测试序列
    step1 关DMOS -> step2 开DMOS -> step3 关CMOS/DMOS -> step4 开CMOS/DMOS -> 回到step1重复测试序列

    用示波器测量芯片 CHG / DSG 引脚信号,相对于B+,DSG信号一直为 -35V左右,CHG信号一直为0V。驱动信号均不受测试序列控制。MOS控制函数 BQ769x2_MosControl(用subcmd) 和 BQ769x2_MosControl_B(写FET_CONTROL寄存器),两种MOS控制方式效果一样,驱动信号不受控


    另外一个现象:当CMOS驱动有输出时(实际测量驱动电压相对B+约10V),把R123去掉,当Q25工作,即CHGD_EN给高电平,CHG信号会被拉到0V(相对B+)。请帮忙确认芯片CHG的驱动能力。

  • 您好,正在询问更了解这款芯片的TI工程师,稍后回复。

  • 您好,建议将gate-source 电阻改为10-MOhm,以最大限度地减少电荷泵上的负载。这听起来像是电荷泵过载 If you check the CP1 capacitor, I would imagine the voltage has collapsed. The charge-pump is only able to handle ~40-uA of constant DC current, while maintaining a decent drive voltage.

    For example, when Q25 is active, you're essentially pulling CHG to GND. If we assume the battery voltage is 50-V, the charge-pump would be ~60-V. 

    When Q25 is ON, the current flow would be 60V/400kOhm = ~150-uA. This would easily over-load the charge-pump alone; this is not even including the additional loads on the charge-pump.

    您可以参考文档 Parallel Paths with the BQ769x2 Battery Monitor