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The device documentation related to the Cyclone 10 LP FPGA states that "you must power up VCCA even if the PLL is not used".

We were comparing the power dissipation of a Microsemi IGLOO2 FPGA with the Cyclone 10 LP. The core power dissipation of the Cyclone 10 LP was significantly lower than the IGLOO2. However, when we measured the VCCA we found that although we were using no PLLs in the design the power dissipation was quite huge on it. So eventually we gave up on the idea to use Cyclone 10 LP in place of the Flash based IGLOO2 FPGA.

Why is VCCA so important? Can't Intel make FPGAs where the device can work with VCCA grounded when PLLs are not being used?

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    \$\begingroup\$ You may get a better response from an Altera FAE or Altera forum. (Especially if you are deciding betveen Altera and a competitor...) \$\endgroup\$
    – user16324
    Commented Apr 30, 2020 at 14:53
  • \$\begingroup\$ You should ask Intel about that. Obviously it powers some other internal structures too. \$\endgroup\$
    – Justme
    Commented Apr 30, 2020 at 14:55
  • \$\begingroup\$ Undriven VCC pins while other VCC pins are driven - sounds like a recipe for dreaded internal latch-up...which might account for excessive internal current drain. \$\endgroup\$
    – glen_geek
    Commented Apr 30, 2020 at 15:11

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At least one reason is that the internal power on reset circuit also monitors VCCA. So it won't come out of power on reset untill all supplies, including VCCA, are detected. The power on reset keeps monitoring VCCA for brownouts to reset it if VCCA sags. But it does not monitor VCCIO for brownouts.

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