Colibri iMX6ULL Issue Tracker

Customer Impact: Some IO pins are powered from the VCC_BATT. Therefore, the high state voltage level might be lower than expected. Any load on these pins can increase the current drain on the RTC battery rail.

Description: The SNVS pins are not powered by the regular main 3.3V rail. They are powered from the VCC_BATT (SODIMM pin 40) rail. Depending on the actual implementation on the carrier board, the VCC_BATT is provided by an RTC battery or over a diode from the regular 3.3V rail. Therefore, the VCC_BATT voltage usually is only around 3.0V (the minimum allowed voltage is 2.4V). This means the maximum output high level of the SNVS pins is also at this level. Any load on the SNVS pin is sourced by the VCC_BATT rail. The current draw on pin 40 could exceed the regular drain on an RTC battery rail.

Workaround: If the RTC feature on the module is not required, connect pin 40 directly to the main 3.3V rail. Maybe an external RTC can be used on the carrier board to keep the time. If the RTC feature is required, make sure the diode between the main 3.3V rail and the pin 40 has a low forward voltage drop and can sustain the current draw. Make sure the peripherals on the SNVS pins are tolerant to the lower voltage level. Try to reduce the load on the pins. Try to avoid using the affected pins. Use other SODIMM GPIO pins instead.

Customer Impact: On rare occasions, a small amount of Colibri iMX6ULL SoMs may fail to communicate with the Ethernet PHY after power-up, rendering the Ethernet interface unusable until the SoM gets power cycled.

Description: The Microchip KSZ8041 Ethernet PHY has an errata: https://ww1.microchip.com/downloads/en/DeviceDoc/80000700A.pdf. According to the second item in the document, a small percentage (less than 1%) of the devices can potentially fail to properly read the strapping pins and set the intended configuration if the 3.3V supply rail rises too fast. On the Colibri iMX6ULL SoM, the 3.3V power rail for the Ethernet rises faster than the required 250us. Therefore, on rare occasions, a small amount of Colibri iMX6ULL SoMs may fail to communicate with the Ethernet PHY after power-up. If the strapping of the PHY configuration fails, the system cannot communicate with the PHY over the MDIO interface. The Ethernet port is not working in this case. According to our tests, the issue mainly appears on the affected modules if the power is enabled at extremely low temperatures (below -30°C). The pull-up resistors of the Ethernet LEDs on the carrier board can backfeed to the 3.3V Ethernet power rail on the module. This backfeeding actually reduces the risk of strapping failures.

Workaround: There is currently no permanent workaround. If the Ethernet PHY is not accessible, try to power cycle the Ethernet PHY or the complete Colibri SoM. Disabling the RMII clock turns off the Ethernet power rails. Try waiting at least 1 second before reenabling the RMII clock and initializing the Ethernet PHY.

Customer Impact: The Ethernet PHY might not exit the power save mode correctly.

Description: Due to the Microchip KSZ8041NL Ethernet PHY errata, the Ethernet can become unusable after exiting the power save mode. The Ethernet PHY is powering down the PLL during the software power down, which can create problems. The issues only appear under certain circumstances and in certain temperature ranges. The issue cannot be reproduced with all modules.

Workaround: Microchip is recommending not using the software power-down of the Ethernet PHY. This means the Ethernet PHY should be left running even in the module's power save (suspend) mode. However, this increases the module's power consumption in the power save state.