Issue
Higher ambient temperatures cause communication malfunctions with XSPI memories.
Details
Our design is heavily adopted from STM32H7S78-DK which also has the same issue described below.
The application uses memory-mapped mode for both Flash and RAM as the main operational units. These memories are configured in the bootloader and everything generated using CubeMX. According to the datasheets, all three components (CPU, Flash, and RAM) are specified to operate reliably under the given conditions, and they do function correctly under normal temperatures.
The problem arises when the ambient temperature increases from 25°C to 60°C. These temperatures are within the acceptable operating range for all components, as stated in their specifications. Upon reaching higher temperatures, the memories start to exhibit failures. However, further investigation revealed that the issue is not with the memories themselves. When the memories alone are heated, they continue to operate reliably, even at elevated temperatures.
The issue was traced to the CPU. When the CPU is heated, the failures begin around 55°C. At this point, the CPU starts to malfunction in its communication with the memories. This leads to the CPU entering an undefined state, with fault reports showing inconsistent and varying results.
Lowering the temperature restores normal operation.
Investigations
- All supply voltages (VCAP, 3.3V, and 1.8V) remain stable during the issue.
- Heating only the memories while keeping the CPU cooled does not cause the problem; the memories operate reliably under these conditions.
- When heating only the CPU, the problem appears immediately, confirming the issue originates from the CPU.
- Same issue happens on STM32H7S78-DK
Specifications
CPU - STM32H7S7L8H6H
XSPI1 - APS256XXN-OBR-BG
XSPI2 - MX25UW6345GXDI00
STM32CubeMX ver 6.13.0
STM32CubeMX package STM32H7RS v 1.1.0
VCC 3.3V
XSPI1 & XSPI2 1.8V
CPUCPLK 600MHz
HCLK 300MHz
XSPI1 & XSPI2 176MHz with no prescaler
