From: Doug Sutherland (wearable_at_earthlink.net)
Date: 2001-12-17 16:03:03
Guys,
I'm placing an order at digikey for building the
ModularEEG. I have a few questions about the parts:
1) Should I be ordering DIP packaging for the ICs?
2) There are two DIP versions of TLC277 op-amps,
TCL277CP and TLC277IP. Which do I need? And
what is the difference? The IP are cost more.
3) There are two versions of AT90S4438P uCs,
AT90S443-8PC and AT90S443-8PI. Which do I need?
4) Assuming I make the programming cable per the
schematic, I don't need a flash tool or one of
those $80 Atmel kits, is that right?
5) There are bunch of different 7.3728 Mhz crystals,
packaging is either cylinder, HC49, or 2-DIP, and
load capacitance of 18pF or 20pF. I'm wondering
if CA-301 7.372M-C 7.3728 MHZ CYL XTAL CA-301 TYPE
is appropriate?
6) Is an LM340T-5.0 1A 5V TO-220-3 Regulator okay?
7) The schematic lists MAX232E. Is that extended
temp version? There is MAX232CPE and MAX232EPE.
8) There are Fairchild and Toshiba 6N139s. Which
ones do you recommend, or does it matter?
9) The only part I can't find at digikey is the
TMA0505S. There sure doesn't seem to be many
pages about this DC/DC converter. Is there an
alternate part that would be suitable? I found
the data http://www.fse-power.com/html/pdf/tma.pdf
but where do I get these things?
10) I will be connecting this EEG to an embedded
PC running off NiMH batteries and powered by
a PT6302A regulator. This is a 5V 3A reg with
high efficiency (~90%). Do you think it would
be safe to power both the PC and EEG from
this single regulator? If so, can I avoid the
TMA0505S and 7805? If not, how can I run both
the PC and EEG off single battery source? It
would be a PITA to have two sets of batteries.
Thanks,
Doug
PS. Sorry for my ignorance on packaging and IC
versions. Some of these data sheets leave
a lot to be desired.
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