Pulling -12VDC from thin air (was Re: MicroVAX II)

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Fri Dec 13 12:21:00 2002

>From: "Ethan Dicks" <erd_6502_at_yahoo.com>
>
>
>--- Jochen Kunz <jkunz_at_unixag-kl.fh-kl.de> wrote:
>> I second that. I know a collector who knows nothing about hardware and
>> how it works.... When I told him that I builded a simple voltage
>> inverter (charge pump) to make the RS232 work on the Sun 4/600 MP he
>> looked like it was black magic to convert +12V to -12V. (The Sun 4/600
>> MP boards needs -12V for the RS232, even -5V are not enough. As I
>> mounted this board in a Sun 3/60 case that doesn't provide -12V, I could
>> not use a serial console.)
>
>Interesting to learn about the 4/600 board and the 3/60 case. Long ago,
>I wondered if the two could work together (I _have_ the 3/60 and I almost
>had the 4/600 board).
>
>If you'd have known to ask, I could have provided you with a +5VDC to
>-12VDC converter module. It's about 20mm x 30mm x 3mm. We had to put
>them on the Qbus COMBOARD because the original design assumed you could
>pull -12VDC off some Qbus pin somewhere, and I suspect that it is not
>the case for all Qbus enclosures (don't know where it is available and
>where it isn't). I have several new on the anti-static mat they shipped
>in.
>
>-ethan
>

Hi
 There is another chip in the MAX232 series someplace
that creates +/- 12 V from 5V for serial uses other that
what a 232 chip is normally used for. It just needs
some capacitors for the charge pumps.
Dwight
Received on Fri Dec 13 2002 - 12:21:00 GMT