Method 4: FPGA

Simplified Power Sequencing (XAPP1375)

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1.1 English

FPGAs are highly configurable and are often used as system controllers as part of a larger board or application. Although power sequencing and power/system management can be achieved with any AMD device, it is best suited to the cost-optimized Artix™ 7 and Spartan 7 device portfolio. The configurable nature of FPGAs allows for easily programming a power-up or power-down sequence in Verilog or VHDL complete with delays and PG checks in real time. FPGAs are highly user configurable and contain a large number of I/Os, and can be configured to include supervisory functions as part of a system controller.

The number of rails that require powering (typically three or four) can be sequenced using a daisy chain method. Many of the topics discussed earlier in this application note apply to FPGAs performing power sequencing. The number of VRMs required, rail groupings, and a simple sequencing method should be taken into consideration during design planning.

Note: Using an FPGA to power sequence a complex system can include an FPGA with a low number of power rails that uses a less intelligent method to sequence itself on power up such as power good daisy chaining.