TI中文支持网Other Parts Discussed in Thread:BQ76942, BQ76952
我尝试用单片机通过IIC协议与BQ76942进行通讯，但是BQ76942的ACK应答非常不稳定。示波器和逻辑分析仪截图如下：
从上面的图片可以看到芯片反馈的ACK信号非常不稳定，甚至连发送器件地址的0x10指令都无法得到稳定的ACK应答（有时应答有时不应答），一次完整的通讯流程都没有完成。
在尝试多次无果后，我将BQ76942取消供电，用板子上的MCU与另一个板子上的BQ76952飞线进行IIC通信，通信一切正常。
逻辑分析仪截图如下：
至此我分析问题可能有两个方向，第一是BQ76942板子的外围电路存在问题，第二是我手中的BQ76942的芯片存在问题。
于是我将另一个板子上的BQ76952芯片吹除，替换上BQ76942芯片，再次使用嫁接IIC的方法进行通信，通信依旧无法正常进行。逻辑分析仪截图如下：
虽然依旧是一次完整的通信都没有完成，但是这次0X10的信号ACK应答率提高了很多，几乎是100%。
我的问题如下：
1：我的bq76942外围电路是否存在问题？
2：BQ76952与BQ76942芯片是否为PIN对PIN关系？可以让BQ76952芯片工作的外围电路，在替换为bq76942后，bq76942是否依旧可以正常工作？
3：在TI的英文论坛中FAE给我的答复是BQ76952与BQ76942在IIC通信协议上是几乎一致的，为什么我使用同样的IIC驱动程序，在两个芯片上结果却不一样？
4：我手中的BQ76942有没有是不良品的可能？
Star Xu：
您好，您的问题在E2E英文论坛已有工程师跟进，请继续关注
e2e.ti.com/…/3692380
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user6630943：
您好！
可能是由于语言沟通的问题，英文论坛的答复不是很能解决我的问题，而且这边的问题描述更加详细，可否在这个中文论坛给予解答？谢谢！
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Star Xu：
您好，请参考下面的内容：
There is a third possibility of some defect in the assembly.
In the schematic:
Then input resistors Rc are 1k, the largest recommended value is 100 ohm. Voltage errors may be apparent, but not if they can't talk to the part.
The bottom of C67 should connect to VSS, not to VC0. This connection can push VC0 below VSS during transients.
The PACK pin should have 10k typical resistance.
Use of REG18 is not recommended. It is the supply for internal circuitry, noise induced into the part can disrupt operation.As noted in the other thread the BQ76942 and BQ76952 use the same circuit for the I2C, if one talks the other talks. Some things to check, you may have already checked these.
Be sure the BQ76942 device installed on the board is an I2C enabled device. BQ76942 and BQ7694202 are I2C, the other available versions are SPI. If it is intermittent that would not be the issue. If the part initially talked and won't talk anymore be sure it was not programmed to a different comm type.
The clock rate looks slow and should be reliable. You also checked that the MCU talks to another device. Since the off-board connection works the MCU portion of the board is apparently good.
The series resistor R97 usually provides a slight shift in the SDA line depending on which device is driving, that should be apparent in the scope waveforms. the instability of the waveform where the BQ76942 should be driving the line low looks like it might have a poor connection. Does the customer have multiple boards and do they all look the same? Have the solder joints been checked on R97 and the IC lead? The R97 value? The continuity of the trace?
Damage could be internal to the part as you indicate. If there are multiple boards, did all go through the same board test? Systematic damage may occur, but one might expect it to also damage the MCU or other components on the SDA line. Has the IC been replaced and does the replacement operate the same?
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user6630943：
XU工您好！我们已经在修改电路准备再次进行调试。感谢您的支持。另外，我看到您在英文论坛转发了我的帖子，其中包括原理图。由于原理图可能涉及公司机密，可否麻烦您将转发帖子中的原理图删除？谢谢！
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Star Xu：
您好，电路已经删除。
