1. Product Description
The product is an automotive remote controller that uses STM32L412RB as an MCU.
The product uses a rechargeable battery and has a power on/off function for storage and delivery.
2. Problem
Some products (0.2%) stop operating due to MCU Latch up during the power-on process when powering on from the power-off state.
Some products stop operating after initial abnormal operation under the same conditions.
The reason why the operation is judged as MCU Latch up is that when the operation stops, MCU Watchdog reset and external reset do not occur.
Only when MCU VDD is turned OFF and then ON, it returns to normal.
3. Self-review
When checking the voltage of the MCU's VDD in the power-off state of the product, it was confirmed that it gradually increased from 0V to 0.35V.
In the power-off state, leakage current occurred due to the connection for the control of the charging circuit, which flowed to the MCU's port (PC13, PA1), causing the MCU's VDD to increase.
During the self-review, it was determined that the defect was caused by the contents of the recently updated Errata 2.2.11.
We received the improvement code of Errata 2.2.11 through the Korean agency and are applying it.
We have not yet received the defective sample from the Vietnamese factory, so we are not able to test it.
4. Inquiry
The issue is being improved in hardware and software with the Workaround of Errata 2.2.11.
1) Why does the issue of Errata 2.2.11 only occur in some products?
The product maintains approximately 0.35V in the same power-off state.
However, the products that have the issue account for approximately 0.2% of all products, making it difficult to detect product defects.
2) Why didn't the issue occur from the beginning?
Our products have been produced and sold since 2019.
The issue was first discovered after 2023.
It has been occurring frequently recently, so the quality team has started reviewing it as an issue.
Looking at the update history of Errata 2.2.11, it was first updated on October 23, 2023, and was additionally updated on November 22, 2024.
Is it related?
I am also asking the Korean agency the same question.
I am also here to get a quick answer.
Thank you.
