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OK to leave Cyclone IV E PLL Power pins grounded or connected to VCCINT?

Altera_Forum
Honored Contributor II
‎06-12-2013 01:27 AM
1,339 Views

I am building a Cyclone IV E design that doesn't use the PLLs. Do I still need to provide a 2.5V power rail for the PLL power pins? Or can I just connect them to ground or VCCINT (1.2V)? 

 

From the Cyclone IV documentation (AN 592: Cyclone IV Design Guidelines): 

"Connect all PLL power pins to reduce noise even if the design does not use all the PLLs—VCCA to 2.5 V 

and VCCD_PLL to 1.2 V or 1.0 V" 

 

This doesn't directly address the case where the design doesn't use ANY PLLs. 

 

It would sure make things easier if I had one less voltage regulator to worry about!
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Altera_Forum
Honored Contributor II
‎06-12-2013 05:44 AM
635 Views

You can't save voltage regulators, because 1.2V and 2.5 V supply are always required. Read the chapter power-on reset circuitry to understand why.

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