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Altera_Forum
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14 years ago

PLL output square wave distorted

I am testing PLL output from an old Stratix board. The PLL has an onboard 80MHz crystal as input clock. However at > 60 MHz, the PLL output is not as square as I wish with ripple and 50mv u...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

I shall borrow a 750Mhz scope to double check the waveform. meanwhile, how do I get a differential pair from the PLL out?

I changed the IO standard for my PLL output pin to Differential-SSTL2, however quartus II complain about:

Error: Can't place enhanced PLL "altpll2:inst23|altpll:altpll_component|pll" in PLL location PLL_5 because I/O cell "Pulsar_Out" (port type EXTCLK of the PLL) is placed in an I/O pin (Pin_B15) which cannot feed port type EXTCLK of PLL location PLL_5

suggestion?