74 series logic but with higher temperature rating? - Page 1
Forum section: electronics / projects

author: MasterBuilder
author_rank: Regular Contributor
timestamp: September 12, 2018, 01:36:35 pm
content: I'm looking for the equivalent of 74 series logic but with higher temperature rating. Some googling reveals that there are parts with the 54 prefix which have a better temperature rating. However they are not easily available to buy for me and are different package sizes. Can anyone suggest an alternative path or logic family or set of parts which have better temperature rating?

author: drussell
author_rank: Super Contributor
timestamp: September 12, 2018, 02:13:42 pm
content: What temperature range are you looking for? Yes, the 54xx series is the original military temperature range version of the 74xx. There was also a short-lived "industrial temperature" version made by TI called the 64xx but it was discontinued in the 1970s.You can also try looking up "automotive grade" versions of parts. They're generally specified for operation from -40 to +125 C and should be readily available these days since they're used here, there and everywhere in automotive applications.

author: MasterBuilder
author_rank: Regular Contributor
timestamp: September 12, 2018, 03:06:54 pm
content: Good tip on the automotive grade versions. I'm aiming for upper temperature rating of +125C.With a bit more searching around it seems the 74 series with the prefix CD rather than SN gives results with higher temperature ratings.

author: MasterBuilder
author_rank: Regular Contributor
timestamp: September 12, 2018, 03:29:21 pm
content: So just discovered Mouser supports wild card searching.As example,searching for **74HC125instead of SN74HC125PWRgives results with better temperature ratings than the SN prefix parts.

author: drussell
author_rank: Super Contributor
timestamp: September 12, 2018, 04:51:04 pm
content: Yeah, do not search with a prefix or you will only find those certain manufacturers, since the prefix is generally the manufacturer's and their licensee's ID code for a particular version and not all manufacturers produce all versions, temperature ranges, etc.Here's a partial list of some common prefixes for various device manufacturers (not necessarily just logic, of course):https://en.wikibooks.org/wiki/Practical_Electronics/Manufacturers_PrefixEdit:Also, on Digi-Key at least, you can search by temperature range in the logic section... Eg. 31 stocked items for a 74HC125 in the MIL (-55 to 125C) and AUTO (-40 to 125C) temperature ranges:https://www.digikey.ca/products/en/integrated-circuits-ics/logic-buffers-drivers-receivers-transceivers/704?k=74HC125&k=&pkeyword=74HC125&sf=1&FV=ffe002c0%2C3f002df%2C3f002e6&quantity=&ColumnSort=0&page=1&stock=1&pageSize=50

author: rsjsouza
author_rank: Super Contributor
timestamp: September 12, 2018, 05:56:41 pm
content: Quote from: MasterBuilder on September 12, 2018, 03:06:54 pmIf you need something higher, scroll down a bit in themain page of the TI logic. There is a section called Q100 logic and translation, which links to some selection guides with Automotive and Military stuff.TI has some suffixes to designate these parts: -Q1 for Automotive and -MIL for military.

author: SeanB
author_rank: Super Contributor
timestamp: September 12, 2018, 06:29:47 pm
content: Just use the regular 74 series, the actual dies inside are the same as the military spec versions, and while they are not warrantied to run at 125C, they will, in almost every case, perform fine. The package itself will operate at that range, though traditionally most came in CERDIP, and these days there are quite a few boutique manufacturers who take a regular 74 series part in a SO package and mount it into a ceramic shell, to make a pin compatible replacement for no longer easily available 54 series devices. They then do the 54 series check cycling and evaluation on them, and in almost every case the devices pass with no problems.The difference between 54 series and 74 series are that the 54 series has **EVERY** device in a lot tested, and there must be zero failure for the lot in the full temperature, voltage and vibration and leak testing, while the 74 series devices are only verified 100% at 25C and 5V00, and the rest are sample tested per lot for the rest of the parameters, and there is a very small allowed failure rate there, in single unit quantities allowed. the 54 series devices are then further screened into tighter spec bins, and for the top grades they all come with a serial number per chip, a full certification sheet ( with traceable standards to international standard measurement references) per device, and a 4 digit price tag per device. Generally only those in space based applications which are classed as "Mission Critical" use them, the rest will be the lower spec devices. Another user is Nuclear use, where they also have extra radiation resistance testing.Just remember as well to read the datasheet, not all parameters are tested during manufacture, many (like drive ability) are only tested per family, and are not tested in production at all after the device is characterised, and then only done every few lots.