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Altera_Forum
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9 years ago

Cyclone 4 ALTPLL wrong freq output

I used EP4CE55F23I7 in a custom board. The problem is that the output of the ALTPLL is wrong. Input clk freq is 50Mhz. ALTPLL output clk freq is around 100KHz although I configured it to an output...
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Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

Hi,

1. Have you checked that pins VCCA, VCCD_PLL, and GNDA are properly connected to power supply?

2. Have you checked noise, riple ect. in those power rails?

3. Have you checked your reference clock with scope?

4. Do you use PLL with parameters generated with megawizard?