Re: gEDA-user: Linear voltregs: Symbol bugs or features?

[Darrell Harmon <mail@xxxxxxxxxxxx>]

On Thu, Sep 22, 2005 at 08:06:13PM -0400, Dan McMahill wrote:
> 
> Lets not even talk about ECL parts where VCC is 0 volts and VEE is -5.2 
> volts.  "Hey, how come all the 10H116's on my board are smokin' hot?"
> 
> Also, mixed supply designs are common.  If you make a 3.3V logic part 
> with implicit "VDD" power and you also have some 1.8V logic which also 
> uses implicit "VDD", you've got problems in the form of a magic smoke leak.
> 
> Implicit power connections are evil!  The only place were I don't think 
> so is DJ's example of the actual ground symbol or an actual VDD symbol. 
>  But there, you're paying attention.
> 
> -Dan
> 

My single board computer has 1.2V, 1.8V, 2.5V, 3.3V, 5.0V and 12V. The
DSPcard is better with "just" 1.2V, 2.5V and 3.3V. Implicit power
connections are something I have never used due to multiple supplies.

I have recently switched to using seperate power symbols for some large
components due to high power and ground pin counts (Spartan 3 FT256 has
28 ground balls and 40 power balls with 3 supply voltages). This works 
well for me and I may even extend it to smaller parts in future designs.

-- 
Darrell Harmon
http://dlharmon.com/dspcard
Credit card size DSP/FPGA board