"vasile" <piclist9@gmail.com> wrote in message news:1189669145.788124.243100@50g2000hsm.googlegroups.com...> On Sep 7, 7:54 pm, Peter Alfke <pe...@xilinx.com> wrote: >> Hi John. >> That's what I suggested in my posting yesterday. >> "Great minds think the same way" :-) >> Peter Alfke >> >> On Sep 7, 9:29 am, John Larkin >> >> >> >> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> > On Thu, 6 Sep 2007 17:23:39 -0500, "Dan K" <danielgkNOS...@visi.com> >> > wrote: >> >> > >Using linear adjustable regulators for VCCINT (1.25v), VCCIO (3.3v), >> > >and >> > >VCCAUX (2.5v). VCCINT and VCCIO are dead on, but VCCAUX is 2.72v, >> > >2.88v, >> > >and 2.92v on the 3 boards I grabbed and measured. All boards seem to >> > >work >> > >just fine. >> >> > >The regulator output voltage is controlled by just 2 resistors. When >> > >I >> > >changed one of the resistors to lover the voltage a bit, VCCAUX did >> > >not >> > >change. This leads me to believe that VCCAUX is somehow being "back" >> > >powered from the Xilinx chip. These voltages are present like this >> > >before >> > >the Xilinx chip has been programmed. I have not removed the regulator >> > >to >> > >measure current yet. Another thought was to put a shotkey diode >> > >between the >> > >regulator output and the load to see if the Xilinx really is powering >> > >VCCAUX, but I thought I'd post and see if anyone else has come across >> > >this >> > >issue. Half the I/O banks are 2.5v and half are 3.3v if that makes >> > >any >> > >difference. >> >> > >Thanks - Dan >> >> > Try adding a "dump" resistor from Vccaux to ground, and see if that >> > pulls the voltage down. >> >> > John- Hide quoted text - >> >> - Show quoted text - > > I'm curious if the original poster has solved the problem in the > indicated way above. > I have a design with Stratix II which has the same behaviour. > > thx, > Vasile >Yes, that was the problem. I had the M0, M1, and M2 pins connected to +3.3 v. As soon as they were disconnected from 3.3v and connected to 2.5v the 2.5v power supply was right on. Dan
VCCAUX too high on a Spartan 3 design
Started by ●September 6, 2007
Reply by ●September 17, 20072007-09-17
