cyclone III power

[Altera_Forum]

Another question. If you look at the Cyclone 3 static power spec in the chart on their web site, it's hard to tell how they pulled 50% out of that. I'm using a relatively small cyclone 2 chip (2C8 in F256), any ideas what I should expect out of the 3C5 or 3C10?

[Altera_Forum]

Guano, try downloading the power estimation spreadsheet for Cyclone 3. It should be pretty easy to do a quick compare.

[Altera_Forum]

Guano Girl, 

 Note that at the low densities the static power isn't much lower than Cyclone II. The big savings in static power come at the larger densities. There may also be some differences in how Cyclone II and Cyclone III burn static power as temperatures increase - once the Cyclone III EPE has been updated for I-temp.

[Altera_Forum]

Hi, 

 There is some circuitry in the device that burns static power independent of the# of LEs in the device. Grabbing the EPE from altera.com (http://www.altera.com/support/devices/estimator/cy3-estimator/cy3-power_estimator.html) is the best way to see this for yourself.  As for temperature dependence, you can see the impact of temperature in the EPE by selecting "User Entered Tj" and typing in the temperature point of interest. Repeat for various temperatures and record the results. Until we release I-specs, extrapolating this curve to 100C isn't a bad guess :-)  Regards,  Paul Leventis Altera Corp.

[Altera_Forum]

When you look at the latest CIII specs, you can see that typical core power is much lower for C3 compared to C2 (for example, typically 3mA for EP3C16 vs 37 mA for EP2C15). Very nice. 

**BUT ** :( , what a pity to see how much C3 PLL consumes compared to core power ( overall PLL consumption is about 38mW typically for an EP3C16, versus 4.8 mW core power !!).  I really wonder why C3 uses 2.5V for powering analog PLL, instead of 1.2V as the C2 does? IMO, this is neither power efficient nor cost efficient (you have to add an 2.5V LDO exclusively for PLL power)  It would be wonderfull to have a next C3 generation, or a derivative, reverting to a single 1.2V power rail for PLL voltages. That would help C3 devices to compete with some other "low power" flash based devices. An other annoying thing is that you have to power these ungry PLLs , even if you don't use any of them. Hey Mr Altera, not all design uses PLL in embedded world :D   A very power conscious user...:rolleyes:

[Altera_Forum]

Hi, 

 That power supply isn't just powering the PLL. There are other circuits dangling off there that contribute to the static power. And in the design of the part, we decided that the benefit of those circuits outweighed the power they consume -- remember, you are still getting power no worse than Cyclone II in the smallest devices, and Cyclone II has signficantly better power than competing devices.  As we get a few CIII devices back from the fab, we'll be adjusting our power specs. I'd hold off passing judgement until we've done so!  Regards,  Paul Leventis Altera Corp.