CycloneV-Fractional N- PLL definitions.

Good afternoon,

I want to produce an output clock (82.5 MHz ) from an incoming Clock (160 MHz) by using of Fractional N-PLL.

I chose "Enable Physical output clock Parameters" option.

Then, I've chosen Fractional N-PLL option at the "Reference Clock Frequency" raw, but immediately I'm getting :

"Error: FPLL_002: The specified configuration causes Voltage-Controlled Oscillator (VCO) to go beyond the limit."

The Reference Clock Frequency located between 50 MHz and 700 MHz.

But when I de-assert "Enable Physical output clock Parameters" option, then previous Error disappears.

What is wrong? Why I cannot change an output clock parameters manually?

P.S. The print-screen with an error and definitions is attached.