Chip doesn't show up in manufacturer's parametric search? - Page 1
Forum section: electronics / projects

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 04, 2019, 07:17:44 am
content: I was looking for some op-amps on TI website and found that OPA627 doesn't show in any parametric search. Yet its listed as an active chip if searched for directly.I am wondering if its just a glitch specific to this particular chip or something chip makers do routinely to phase out older designs? Is it actually better to do parametric search on something like Digikey instead of manufacturer's site?

author: Kleinstein
author_rank: Super Contributor
timestamp: May 04, 2019, 08:04:54 am
content: I also noticed that the search sometimes did not show some chips - in my case audio grade OPs like OPA1642 and similar.There are quite a few extra parameters and some may exclude some chips. Anyway the search seems to change from time to time so it may be already be different now. With older parts it may happen they enter wrong data in the lists. I don't think they intentionally skip the older parts - they may be just miss some properties in the database (e.g. package family, type (BJT,JFET,CMOS), price). Ideally they would put the old parts to the bottom of the list.The search at the distributors is also not always that convenient. The main problem there is the way the supply voltage range is handled - a long list with lots of ranges (e.g. 3 - 12 , 3.3 - 6 , ... is not practical at all). In addition there seem to be quite some errors in those lists - it mainly gets obvious when you get parts shown that do not fit at all, but one would likely also miss some due to wrong entries. The big advantage at the distributors is that one gets parts from different sources including some of the less common ones (e.g. ST, Toshiba, Samsung).

author: Ian.M
author_rank: Super Contributor
timestamp: May 04, 2019, 09:51:55 am
content: GIGOhas been a problem in large collections of data for over 150 years*and component manufacturers and distributors parametric databases are far from immune. e.g. Microchip's database underlying their MAPS parametric search and their various product range selectors is well known to be heavily contaminated with bad data - this is obvious as large portions of it can be accessed as CSV spreadsheets from the product range pages and in many cases a part isn't even entered in the correct product range.Voltage ranges are -in theory- quite easy to handle in web based parametric searches. A single or multiple item selection can never be satisfactory. Instead the max. and min. voltages must be stored in the database and the user allowed to set upper and lower limits for each as search criteria. However the managers who sign off on the parametric search U.I. development typically have never used a soldering iron, so engineers continue to get almost unusable parametric search engines foisted on us by MBAs.*Charles Babbagein his 1864 book"Passages from the Life of a Philosopher"Quote

author: Zeyneb
author_rank: Regular Contributor
timestamp: May 04, 2019, 02:40:30 pm
content: I've a positive experience with the Digikey website to find parts I'm interested in. Sure, not all data is correct, but it's obvious to me Digikey really strives for perfection regarding this. If you find something incorrect and when you can back this up with information from the manufacturer they are very eager to correct it soon. Just leave them a short message. Maybe you will help a fellow Eevblog forum member also by doing so.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 05, 2019, 04:28:37 am
content: Yes, Digikey seems to have the best for parametric search compared with other distributors. The voltage range is annoying. it seems the best solution is to select all other parameters first and then pick a few choices for the voltage range.

author: David Hess
author_rank: Super Contributor
timestamp: May 05, 2019, 11:03:16 am
content: I have noticed the same thing with TI's web site going back many years. It seems to favor more recent and expensive parts over older and less expensive parts which are still in production. In many cases, the only reason I was able to find a currently produced but old part was because I already knew the part number or was able to find it in other documentation.I suspect this behavior is deliberate on their part simply to steer customers to more expensive parts.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 05, 2019, 12:18:11 pm
content: OPA627 is actually quite expensive, $25 per chip, at least through the major distributor channels. Perhaps the reason in that case is that they have few major customers and want to run the production as infrequently as possible.But it seems that one shouldn't trust TI website for a complete list of their own chips.

author: David Hess
author_rank: Super Contributor
timestamp: May 05, 2019, 12:51:31 pm
content: Quote from: maxwell3e10 on May 05, 2019, 12:18:11 pmBurr-Brown always charged a premium but that is excessive. I suspect the high cost comes from being fabricated on an old process.Analog Devices' version, the ADA4627, is $8 but not available in the DIP package. I am not aware of any other direct replacements without knowing more about the application. There are no comparable CMOS parts.QuoteI have not trusted TI's selection guides for years because of missing parts.

author: Yansi
author_rank: Super Contributor
timestamp: May 05, 2019, 12:58:14 pm
content: Quote from: David Hess on May 05, 2019, 11:03:16 amI second that.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 05, 2019, 01:01:17 pm
content: For OPA627 there are a few listed on e-bay. I wonder if they are real or fake:https://www.ebay.com/itm/5pcs-OPA627AP-OPA627-Precision-High-Speed-Difet-DIP-8/251728025314?hash=item3a9c28d6e2:g:mgMAAOSwiCRUcC6Bhttps://www.ebay.com/itm/5pcs-OPA627BP-OPA627-precision-high-speed-op-amp-DIP-8/170962971791?hash=item27ce2fec8f:g:AJAAAOxypthRw8di

author: Kleinstein
author_rank: Super Contributor
timestamp: May 05, 2019, 01:33:51 pm
content: Quote from: David Hess on May 05, 2019, 12:51:31 pmThe OPA627 is a DI isolated JFET OP - so it's a kind of special process, in my understanding a little like SOI. The really special feature is the low input bias. The low input bias also needs relatively expensive testing for low leakage. The offset trimming can also make old designs expensive.If a little more bias can be tolerated the OPA140 or OPA827 might be an alternative.

author: jaromir
author_rank: Unknown
timestamp: May 05, 2019, 01:57:01 pm
content: Quote from: maxwell3e10 on May 05, 2019, 01:01:17 pmNot sure, but there is known history of "not-that-exactly-real" OPA627's from cheap sourceshttps://zeptobars.com/en/read/OPA627-AD744-real-vs-fake-china-ebay

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: May 05, 2019, 02:15:39 pm
content: Quote from: jaromir on May 05, 2019, 01:57:01 pmInteresting. So they are probably fake!