[SI-LIST] Re: output circuit for 68000 NMOS driver
- From: Sandy Taylor <cmos@xxxxxxxxxxxxxx>
- To: james.f.peterson@xxxxxxxxxxxxx
- Date: Fri, 31 Jan 2003 17:09:29 -0800
Jim
The output driver uses nfets for both pull up and pull down.
Voh is not as good as using a depletion device due to the VT loss,
but it avoids the large current that a depletion pull up device
would waste when the output is low. The depletion mode devices
are used in the logic gates as a resistive pull up.
This is going way back in history, but as I remember
for 5V operation the levels looked like:
Vil 0.8V
Vih 2.0V
Voh 2.4V (maybe at 200uA)
Voh 0.4V (maybe at 1.6 mA)
Some signals had higher driver currents.
I hope this helps. What are you doing with NMOS devices?
Sandy Taylor
CMOS Solutions
Olga Wa
Peterson, James F (FL51) wrote:
>
> Hello,
>
> I have been looking for information on the drivers of an old 68000
> processor. The users manual says these outputs are NMOS technology but I
> don't have any information on the topology or circuit configuration of NMOS.
> Someone mentioned that it was "depletion mode NMOS".....
>
> I'm looking for details of the outputs (circuit config., Voh (min, and typ),
> functional description, etc.). Anybody's help would be much appreciated.
>
> Jim Peterson
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