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Altera_Forum
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16 years ago

Cyclone III, huge cap at VCCD_PLL

Hi All! Altera document "Cyclone® III Device Family Pin Connection Guidelines PCG-01003-1.0" says that 470 uF capacitor must be used at digital power of PLL (besides a lot of ceramic capacitor...
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Altera_Forum
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16 years ago

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What is the reason for using of such capacitor in VCCD_PLL circuit?

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It doesn't sound reasonable. None of Cyclone III I'm working with has a similar capacitor. In my opinion, it should be expected, that the device manual is containing all respectice information. It tells

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VCCD_PLL must always be connected to VCCINT through a decoupling capacitor and ferrite bead.

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The suggestion is also varied to "should always" in some places. Both versions sound reasonable.