From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2001-12-16 16:03:21
Hi Doug,
----- Original Message -----
From: Doug Sutherland <wearable_at_earthlink.net>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Saturday, December 15, 2001 8:40 AM
Subject: [buildcheapeeg] Re: DS275 RS232 Level Converters
> Ooops ... wrong URL ... here is the DS275 data sheet
> http://pdfserv.maxim-ic.com/arpdf/DS275.pdf
>
> Doug Sutherland wrote:
>
> > Guys,
> >
> > It was mentioned more than once that MAX232 draws too much
> > current to be powered by the PC serial port. I wonder if
> > DS275 might be good for this, seems to be low power. I have
> > used these instead of MAX232 with very good results. I like
> > how they are small (8-pin DIP) and require no external caps.
> > Check the data sheet and let me know what you think.
Seems to be a nice low-power alternative to MAX232 besides the
non-standard output voltage.
However at the moment the voltage supply concept with the DCDC
converter TMA0505S provides unlimited power for the interface
(because it uses power from the PC-side via gamport or AC/DC adaptor)
One issue about the DCDC converter is isolation voltage:
The TMx-Series (http://www.tracopower.com/products/tma.htm)
comes in 3 isolation grades:
TMA: 1000 VDC
TMV: 3000 VDC
TMV-EN: 250Vrms working voltage, 3000Vrms, 6000Vpk
I assume the TMV0505EN should provide sufficient protection:
The brainmaster specifications say:
www.brainm.com/productinfo/bmr2emodule/systemspecs/systemspecs.html
...
Isolation: optically isolated to 130 volts (continuous) or 1500 V (1 sec)
...
The TMV-EN would provide twice of the BM isolation.
So I conclude that the BM is not IEC601-1 approved
(because that would require 5500V isolation)
On the other hand however the BM is FDA approved.
That means, there must be another norm that is
much simpler to comply to get the FDA approval.
Regards,
Joerg
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