instrumentation amps

M

Mook Johnson

Guest
I'm using the AD620 WAY outside of its temperature range and there are
non-linearities that are cropping up.

I've looked and there are several pin compatable drop-ins from Linear and
TI(BB) that have very similar specifications.

My question is if anyone knows if these are three independant designs or did
the same guy bounce from company to company and carbon copy the same silicon
for each?
 
Hello Mook,

I'm using the AD620 WAY outside of its temperature range and there are
non-linearities that are cropping up.

I've looked and there are several pin compatable drop-ins from Linear and
TI(BB) that have very similar specifications.

My question is if anyone knows if these are three independant designs or did
the same guy bounce from company to company and carbon copy the same silicon
for each?
Click to expand...
Maybe just a 2nd source agreement. There are companies and engineers
(like me...) who are very hesitant to design in single sourced parts. In
mission critical apps 2nd source is usually mandatory or you aren't
allowed to design it in.

Regards, Joerg

http://www.analogconsultants.com
 
Would you guess that tha die are duplicates of each other of two seperate
approaches to achieve the very similar specifications.

Say Analog uses its opamp silicon design to make the in-amp on a single die,
but Linear and TI uses their own with different opamp silicon but achieving
the same perforance specification.

I know the AD620 for 1X gain has a 1.5% gain reduction at high temperatures
(far above datasheet rating). Its flat out to about 10C south of my max
temperature. Then the gain drops sharply down -1.5% at max temp (>125C).

Those silicon resistors leaking maybe?

I'm considering testing other "2nd source" parts to see if they "hopefully"
do this at higher temperature or (lucky lucky me) don't drift at all due to
a different die process. If they are dupes, likely the answer will repeat.





"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:neUHe.787$C11.541@newssvr21.news.prodigy.com...
Hello Mook,

I'm using the AD620 WAY outside of its temperature range and there are
non-linearities that are cropping up.

I've looked and there are several pin compatable drop-ins from Linear and
TI(BB) that have very similar specifications.

My question is if anyone knows if these are three independant designs or
did the same guy bounce from company to company and carbon copy the same
silicon for each?

Maybe just a 2nd source agreement. There are companies and engineers (like
me...) who are very hesitant to design in single sourced parts. In mission
critical apps 2nd source is usually mandatory or you aren't allowed to
design it in.

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
 
Hello Mook,

Would you guess that tha die are duplicates of each other of two seperate
approaches to achieve the very similar specifications.

Say Analog uses its opamp silicon design to make the in-amp on a single die,
but Linear and TI uses their own with different opamp silicon but achieving
the same perforance specification.
Click to expand...
No idea on this one. It is all a matter of contracts between them and
that could include mask sharing. Those contracts are sometimes necessary
when a potential large volume customer made the design-in of a part
contingent upon 2nd sourcing. It is amazing to sit in the room when two
Goliaths who would normally tear each other apart gather around the same
table.

I know the AD620 for 1X gain has a 1.5% gain reduction at high temperatures
(far above datasheet rating). Its flat out to about 10C south of my max
temperature. Then the gain drops sharply down -1.5% at max temp (>125C).

Those silicon resistors leaking maybe?

I'm considering testing other "2nd source" parts to see if they "hopefully"
do this at higher temperature or (lucky lucky me) don't drift at all due to
a different die process. If they are dupes, likely the answer will repeat.
Click to expand...
I think Jim (Arizona) would be the expert here. I always did my high
temp stuff with discretes.

Regards, Joerg

http://www.analogconsultants.com
 
Say Joerg,

I've heard the "must have a second source" line from you before, and I've
often been curious... just what do you do for any reasonably complex IC such
as a DSP, FPGA, CPU, Ethernet controller, etc.? Since -- other than really
old parts -- no one makes second sources.
 
Page 13 of the Analog Devices data sheet for the AD620 reads as if they
thought they'd invented something.

Page 11 of the Linear Technology data sheet for the LT1168 looks very
similar .... Page 11 of the Burr-Brown (now Texas Instruments) data
sheet INA337 is less specific, but could well be describing the same
structure. Note that the INA337 is specified over the automotive
temperature range -40C to +125C.

It is unlikely that one designer bounced from company to to company -
Linear Technology is in Silicon Valley, California (Milpitas, Ca
95035-7417), Analog Devices is in Massachusetts (Norwood, MA
02062-9106) and Burr-Brown was in Tucson, Arizona before they got taken
over by Texas Instruments - Jim Thompson probably knows all about them
....

-----------------------
Bill Sloman, Nijmegen
 
Hello Joel,

I've heard the "must have a second source" line from you before, and I've
often been curious... just what do you do for any reasonably complex IC such
as a DSP, FPGA, CPU, Ethernet controller, etc.? Since -- other than really
old parts -- no one makes second sources.
Click to expand...
Sometimes we have to bite the bullet and use them. For example, one of
the future designs here may contain an MSP430 which won't have a 2nd
source for years or probably forever. There are companies I trust more,
some I trust less and some I don't trust at all (and won't design in any
single source part from them).

Also, we take a very careful look at where a certain specialty part is
used elsewhere. If it's consumer the scrutiny will be even higher
because those products can fall from grace in no time and then the
components in there will as well. Video or graphics cards are a perfect
example here. Once I was very tempted to use a controller for that
market. Thank God I resisted. Not only the part but the whole company
pretty much vanished.

Other than that, if there is a single source part and there is a way to
design the circuitry discrete at same or lower cost it will be designed
discrete, with jelly bean parts.

Regards, Joerg

http://www.analogconsultants.com
 
On Tue, 02 Aug 2005 23:34:16 GMT, "Mook Johnson" <mook@mook.net>
wrote:

I'm using the AD620 WAY outside of its temperature range and there are
non-linearities that are cropping up.

I've looked and there are several pin compatable drop-ins from Linear and
TI(BB) that have very similar specifications.

My question is if anyone knows if these are three independant designs or did
the same guy bounce from company to company and carbon copy the same silicon
for each?
Click to expand...
Only two possibilities:

(1) Linear and TI are licensed by Analog Devices to replicate the
parts.

(2) Linear and TI have their own designs meeting the specification
(most likely scenario).

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
I doubt the same IC designer hopped that many companies. He would have
had to sign non-disclosure agreements anyway, to protect company B from
getting company A's trade secrets -- at least for a year or so.

My advice -- if you have to use the AD620 at a higher temp, go with the
AD620S. It cost's a "bundle" but I use it all the time in my line of
work (spacecraft/launch vehicle avionics).
 
In article <YpTHe.59863$gL1.11484@tornado.texas.rr.com>,
Mook Johnson <mook@mook.net> wrote:
I'm using the AD620 WAY outside of its temperature range and there are
non-linearities that are cropping up.

I've looked and there are several pin compatable drop-ins from Linear and
TI(BB) that have very similar specifications.

My question is if anyone knows if these are three independant designs or did
the same guy bounce from company to company and carbon copy the same silicon
for each?
Click to expand...
What _is_ pretty likely is that they are all using similar processes,
i.e. the "parts" within all the ICs will have similar characteristics
such as TCs.

To get different overall specs, you have to go to parts made with different
technologies or at least different dopants, etc.

-frank
--
 
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