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Problem with ALTPLL

Altera_Forum
Honored Contributor II
1,496 Views

I use a ATLPLL IP In my design. This PLL has one input clock and one output clock. 

The input clock is 62.5MHz. The PLL outputs an inverted clock. 

I expected the clock max skew from inclk0(62.5MHz) to c0(inverted) is 0.5ns. 

The post-sim waveform shows the skew is 10.7ns. 

The ALTPLL's connections as below: 

DPLL U_DPLL( 

.inclk0 (clk_62M ), 

.c0 (clk_62M_inv), 

.locked (locked ) 

); 

What's wrong with my design?  

Any and all help is very much appreciated 

Harris
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Altera_Forum
Honored Contributor II
788 Views

Is PLL output configured as source synchronous?

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Altera_Forum
Honored Contributor II
788 Views

How to configure the PLL's output? 

Thanks
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Altera_Forum
Honored Contributor II
788 Views

Quartus II MegaWizard Plug-In Manager

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Altera_Forum
Honored Contributor II
788 Views

OK 

I will try it. 

Thanks
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Altera_Forum
Honored Contributor II
788 Views

I have changed the PLL settings, but the problem is still exist. 

My PLL current settings:  

1. Use the feedback path inside the PLL 

2. In normal mode 

3. The source synchronous compensation mode si disabled by Quartus II  

The c0 is used internal. 

Thanks
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Altera_Forum
Honored Contributor II
788 Views

I believe Cris suggets to set it to source synchronous mode instead of normal mode (tick the selection just under normal mode)

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Altera_Forum
Honored Contributor II
788 Views

The option In source-synchronous compensation mode is disabled by Quartus II.  

I can not tick the selection. 

My device is Cyclone. 

Thanks
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