Apple SCSI TermPWR; Was Re: This is funny (ebay)

From: Richard Erlacher <edick_at_idcomm.com>
Date: Mon Feb 25 09:24:26 2002

It's not particuarly important as far as its function is concerned, since the
forward voltage is just another factor that has to be taken into account in
the design of the TermPwr circuit. What's more, there's no place where it
says it has to be a silicon diode, since it could be a schottky diode with
only 0.2 volts of Vf anyway. Most of the time, however, I'd suspect it's a
mosfet that's enabled by a jumper setting. That will have some forward
voltage loss due to its resistive nature, but not terribly much at the small
currents, normally used for TermPwr. Modern MOSFETs have an on-resistance
well under 0.1 ohm.

Dick
----- Original Message -----
From: "Stan Barr" <stanb_at_dial.pipex.com>
To: <classiccmp_at_classiccmp.org>
Sent: Monday, February 25, 2002 1:26 AM
Subject: Re: Apple SCSI TermPWR; Was Re: This is funny (ebay)


> Hi,
>
> "Richard Erlacher" <edick_at_idcomm.com> said:
> > Apple probably left out the
> > diode so they wouldn't have to put in the fuse.
> >
>
> Also a silicon diode will lose 0.6 - 0.7 Volts, which may or may
> not be important...
> --
> Cheers,
> Stan Barr stanb_at_dial.pipex.com
>
> The future was never like this!
>
>
>
Received on Mon Feb 25 2002 - 09:24:26 GMT