[Coco] 6809/6309 Power Analysis

[jdaggett at gate.net]

Stephen

The OUTPUT portion of the I/O pins are NMOS depletion mode FETs. Essentially you have a 
FET that has the drain fed through a NMOS Diode (FET with the gate tied to the drain) These 
are rather small geometry diodes and transistors so the current source and sink capabilities 
in rather limited. 

The output FET Drian diode is tied to same VCC that powers the chip.  There may also be a 
current source mirror circuit that feeds the output transistor.

james 

On 21 Jan 2010 at 17:05, Stephen Adolph wrote:

> I gotta say, I think this can be a challenge to define, let alone measure.
> 
> Certainly there is the dynamic supply power that is feeding the
> toggling gates.  This is coming from the main supply.  I would just
> measure the power on the main lead.
> 
> But, there is also power related to I/O.
> 
> I'm sure there is an industry standard technique and definition of
> what and how to measure this, but I'm not aware of it.
> 
> I would probably just do the main supply lead and assume it is the
> majority of the power.
> 
> ...Steve