16 Jun
2010
16 Jun
'10
10:34 a.m.
I'm working on a controller to drive some long >1m bidirectional
lines that require 220/330 termination and 48 ma. drive current
capability. For sake of argument, call them SCSI-1 SE (but they're
not SCSI (or HPIB)).
I'm finding that my choices are pretty limited. I could use a
74F621, 74FCT621 (CMOS) or a good old 75160. All appear to be within
the same approximate price range.
Can anyone make any recommendations?
Thanks,
Chuck
16 Jun
16 Jun
11:13 a.m.
From: cclist at sydex.com
To: cctalk at classiccmp.org
Date: Wed, 16 Jun 2010 10:34:42 -0700
Subject: OC/OD 48 ma transceivers
I'm working on a controller to drive some long >1m bidirectional
lines that require 220/330 termination and 48 ma. drive current
capability. For sake of argument, call them SCSI-1 SE (but they're
not SCSI (or HPIB)).
I'm finding that my choices are pretty limited. I could use a
74F621, 74FCT621 (CMOS) or a good old 75160. All appear to be within
the same approximate price range.
Can anyone make any recommendations?
Thanks,
Chuck
Hi Chuck
You can always parallel outputs of something like a '244 or
similar. I've done this in the past when I needed more drive.
The CMOS versions share well but the TTL versions don't.
I found that if using TTL, I had to over spec by 100% to get
good sharing while the CMOS I found about +25% worked quite well.
Dwight
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12:30 p.m.
On 6/16/10 10:34 AM, Chuck Guzis wrote:
I'm working on a controller to drive some
long>1m bidirectional
lines that require 220/330 termination and 48 ma. drive current
capability. For sake of argument, call them SCSI-1 SE (but they're
not SCSI (or HPIB)).
I'm finding that my choices are pretty limited. I could use a
74F621, 74FCT621 (CMOS) or a good old 75160.
you probably want to use a slower part (ls641) for a cable driver.
1:34 p.m.
On 16 Jun 2010 at 12:30, Al Kossow wrote:
you probably want to use a slower part (ls641) for a
cable driver.
48 ma. is the stumbling block there--ISTR that LS is rated for 24 ma.
AS/S/F/FCT are all rated for 48.
Futurlec has the 75160B for $1.90 the each, so I'm inclined to go
that way.
Dwight, I could parallel a 244, but that'd double the package count
and not be OC, so I'm less inclined to take that approach.
--Chuck
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