CY7C68013A无法从Eeprom读取固件

在我们最近的大规模生产中，我们发现该装置的小部分（2%）（使用CY7C68013A）没有。
在一定条件下从EEPROM读取固件。只有当用户插入USB电缆时，才会发生这种情况。
从设备到设备的电源，并快速将它重新插入（例如在5秒内）…注意到我们观察到了
主功率（包括5V、3.3V和其他），它们都在1秒（当关闭时）下降到GND，并且在板上。
电压监视器将复位MCU（CY7C68013A），当3.3V VCC达到2.8V（上电时）…当出现这样的问题时，
电源，复位，时钟到CY7C68013都很好，但是我们没有观察到I2C总线上的I2C脉冲（正常）。
启动，很多这样的I2C设备插入在活动时，单片机读取固件从EEPROM）。
如果我们等待更长的时间（后关闭），如20秒，这样启动失败率较低的问题了如果等待…
为30秒（和插头回）。
注：
1）。这样的问题只出现在设备的次要部分（2%）。
2）。对有问题的设备，它具有率（如50）显示的问题甚至我们做一个快速的塞子/。
3）。对有问题的设备，如果我们等待更长的时间后关闭（然后插上），率太低。
我知道这可能是PCBA硬件相关的问题（例如焊接问题），但我的问题是什么能让
CY7C68013A卡在引导装载程序无法读取外部EEPROM固件。
谢谢！



     以下为原文
   In our recent mass production, we found that there're minor part (~2%) of the device (using CY7C68013A)  doesn't
read firmware from Eeprom on certain conditions. That only happens if user plugs off the USB cable (which also provides
power to device) from the device and quickly plug it back on (e.g. within 5 seconds)...Note that we observed
the main powers (including 5V, 3.3V and others), all of them are down to GND in 1 second (When plug off), and the on board
voltage monitor will reset the MCU (CY7C68013A) when the 3.3V Vcc reaches ~2.8V (When power on)...When such issue occurs,
the Powers, Reset, Clock to CY7C68013 are all good, but we didn't observe any the I2C pulses on the I2C bus (on normal
booting, there're many such I2C activities when device is plugged on and the MCU reads firmware from Eeprom).
     If we wait for longer time (after plug off), e.g. 20 seconds, such booting fail rate is lower...the issue was gone if waiting
for 30+ seconds (and plug back).
     Note:
     1). Such issue only show up on minor part of the devices (~2%).
     2). For a problematic device, it has rate (e.g. 50%) to show the issue even we do a quick plug off/on.
     3). For a problematic device, if we wait longer after plug off (and then plug it on), the rate is much lower.

     I understood that this might be the PCBA hardware related issue (e.g. soldering issue), but my question is what might make
the CY7C68013A is stuck in the boot loader and can't read firmware from external Eeprom.

Thanks!