8.4.20 Single Event Upset

A single event upset (SEU) is a change-of-state caused by the free charge created by the ionization. The UCD90320U device uses ULA particle emission mold compound to reduce the soft errors - FIT(failure in time) number caused by the Alpha Particles. Moreover the following algorithm is adopted to detect SEU in the SRAM containing the static user configuration configured from Fusion Digital Power Designer software. Both ULA mold compound and SEU detection provide higher reliability for the applications.

The device scans configuration memory within approximately six seconds. When the device detects an SEU, the device takes these actions.

• A device attempts to correct this change-of-state by copying the data stored in the data flash. But if the customer changes the settings on-the-fly and has not saved those changes into the data flash, the correction may not be successful.
• The device uses MFR_STATUS bit 14 to indicate an SEU event and a PMBUS_ALERT bit triggers when it detects an SEU. The Fusion Digital Power Designer software has an option to prevent this event from triggering a PMBUS_ALERT signal.
• The SEU bit in the MFR_STATUS does not clear automatically even after the SEU state corrects. The bit clears only when the device is resets, when the device cycles power or when the host issues a clear fault command. The device sets the status bit again if the SEU remains present after the host issues a clear fault command.
• The device logs an SEU event with the corrupted memory address. The application has the option to disable the detail logging for an SEU event.
• The device logs one SEU event per device reset or device reboot. The device does not re-log an SEU event after the application issues clear fault command to clear existing fault log.