1.2 Single Event Effects Immunity of FPGA Configuration Cell

Malfunctions in Integrated Circuits (ICs) due to radiation effects (single event effects) from high energy neutrons at ground level and high altitudes are a major concern for safety-critical applications.

Configuration upsets in FPGAs are problematic because the configuration memory must remain static and error free during all the operating hours of the device for correct operation. Any upset will be persistent until the device is powered-down or the cell is reprogrammed correctly. If an upset occurs in the erroneous state, the logic or routing of the FPGA fabric will be wrong, potentially causing not just a single wrong data value, but a string of wrong results until it is fixed. This may require a full system reboot.

Figure 1-1. Configuration Upsets in SRAM FPGAs due to Single Event Effects

Attempts to mitigate configuration upsets in SRAM FPGAs are extremely complex. Typically, they require dual-redundant FPGAs with an external controller, which periodically searches for configuration errors in each SRAM FPGA and initiates a failover from primary to secondary FPGA while reprogramming of the primary FPGA takes place. This presumes that the system will not be detrimentally affected by the bad data produced by the FPGA during the period that the configuration SEU is undetected. It also presumes that the system can tolerate the subsequent loss of processing while the failover from primary to secondary takes place.

The PolarFire FPGA configuration is SEE immune because of the non-volatile technology, unlike the configuration memory in SRAM-based FPGAs, which can flip state due to neutron hits. In the PolarFire FPGA family, the SONOS NV charge is stored in the nitride dielectric, which is not susceptible to charge loss from neutron hit, making it immune to Neutron induced configuration upsets.

Figure 1-2. SEE Immunity of PolarFire FPGA Configuration Cells

The first phase of neutron testing is performed on PolarFire FPGA family. The main objective is to test the product for latch-up behavior and to get soft error data on the fabric. For test results, see TR0043: PolarFire Neutron Test Results Test Report.

For more information about radiation effects, see www.microchip.com/en-us/products/fpgas-and-plds/reliability.