The Pin Connection Guideline states the following, but 800kHz and 1MHz is not required as long as the FPGA power requirements are met.
Altera® MAX® 10 FPGA Device Family Pin Connection Guidelines
https://docs.altera.com/max-10-fpga-device-family-pin-connection-guidelines
(search for Low Noise Switching Regulator)
(excerpt)
The switching frequency is usually between 800kHz and 1MHz and has fast transient response.
The switching frequency range is not an Intel requirement.
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Category: Power Supplies
Tools: -
Devices: MAX® 10