16 Nov
2015
16 Nov
'15
11:27 a.m.
On 11/16/15 8:21 AM, Noel Chiappa wrote:
So, I have bought a number of DS8641 bus transceivers
from a source in China,
and cognizant of the claims that there are a lot of counterfeits coming from
China, how can I test them to make sure the meet specs?
I have a QBUS test board which I have constructed (it's basically just a
single read/write register), so I can verify their _basic_ functionality; but
the UNIBUS/QBUS specs give a number of analog qualifications, and it's those
I'd like to check.
Some of them I can figure out how to test, although a couple of them would
seem to need special test rigs, e.g. input high threshold of 2.5V and low
threshold of 1.4V, but I _think_ I can work out how to test those - a board
with a pot on it, so I can vary the input voltage, and see where the output
switches. (I'm not necessarily going to test every last chip, but I'd like to
do random samples.)
However, there are others of which I'm not at all clear how to test, e.g.
output high leakage current of 25 uA. How would I test that? (And replies of
the form 'use such and such an approach' probably aren't detailed enough for
me - my analog-fu is pretty weak - so details would be most greatly
appreciated! ;-)
A number of data books have circuits that were used to measure the
parameters (including
rise/fall times) so you might want to look at some of them (substituting
values for the 8641
vs the part in the data book). They all look to be about the same as
far as testing goes
(except for parameters obviously). Just look for parts that are as
similar as possible in terms
of input/output configurations (ie don't use a test configuration that
was spec'd for totem
poll outputs vs open collector, etc).
TTFN - Guy