Need PTH equivalent of 74AHC  - Page 1
Forum section: electronics / projects

author: scott216
author_rank: Regular Contributor
timestamp: December 12, 2014, 08:45:30 pm
content: I was reading Paul Stoffregen's article onbetter SPI bus designand he recommend using a tri-state buffer chip and shows how on an Adafruit product they us a 74AHC1G125. I'm looking for a through hole version of the 74AHC1G125 for my project. I don't know anything about buffer chips so I'm not sure how to pick one on my own. On Digikey I didn't see a through hole version of the 74AHC series chip - except 14-pin DIP. Can someone recommend an 8-pin DIP chip for this application?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 12, 2014, 09:46:27 pm
content: Not knowing exactly what you're doing with it, I'd guess a 74HC model would be fine. It's going to be a quad. Whatever devices are unused, ground their inputs so they aren't floating.Tim

author: rob77
author_rank: Super Contributor
timestamp: December 12, 2014, 09:56:03 pm
content: i doubt you will find the modern AHC(T) versions in through holethe older HC(T) and AC(T) are common in THT but the new ones are mainly (only?) SMT.

author: marshallh
author_rank: Unknown
timestamp: December 12, 2014, 09:56:59 pm
content: Hope you're not going to be using a breadboard. What's the problem with smd?

author: w2aew
author_rank: Super Contributor
timestamp: December 12, 2014, 10:55:04 pm
content: Quote from: scott216 on December 12, 2014, 08:45:30 pmI doubt you'll find any "single gate" versions in a DIP package. If you must got PTH, then use the regularly available quad parts and simply not use the unused gates (but use pull up/down on unused inputs).

author: Zero999
author_rank: Super Contributor
timestamp: December 12, 2014, 11:26:20 pm
content: Yes, you won't find the 74AHC1G125 in through hole. Omit the 1G part of the number and you have the quad, which is available in through hole.http://www.digikey.com/product-detail/en/SN74AHC125N/296-4531-5-ND/375724The whole point of the 1G parts is to save space, hence why they're all SMT.

author: scott216
author_rank: Regular Contributor
timestamp: December 13, 2014, 03:02:57 am
content: Thanks for the info. Looks like if I want to stick with through hole I have to use a bigger chip. I could use SMT, but I'm making my PCB on my Shapeoko CNC mill and it's a bit easier to make boards with through hole parts.I'm using it with a Moteino - which is like an Arduino Uno with a radio and an Wiznet Ethernet module.

author: nctnico
author_rank: Super Contributor
timestamp: December 13, 2014, 05:16:36 pm
content: If it has to be 8 pin dip you can consider using an RS485 driver chip in 8 pin DIP package.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 13, 2014, 06:54:24 pm
content: Remember you only need it for devices that don't tristate their output when unselected, which isn't very common.

author: scott216
author_rank: Regular Contributor
timestamp: December 13, 2014, 09:03:59 pm
content: Quote from: mikeselectricstuff on December 13, 2014, 06:54:24 pmIs there a way to test my device to see if it tri-states or not?Edit -I found the answer to testing tri-state in the article I linked too in the original post. I forgot that it said how to test for tri-state behavior.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 13, 2014, 09:26:07 pm
content: Quote from: scott216 on December 13, 2014, 09:03:59 pmRead the datasheet!

author: scott216
author_rank: Regular Contributor
timestamp: December 13, 2014, 09:41:05 pm
content: Quote from: mikeselectricstuff on December 13, 2014, 09:26:07 pmI'm using an Ethernet module from sparkfun and it used a Wiznet 5100 chip. The data sheet for the wiznet sheet is:http://www.sparkfun.com/datasheets/DevTools/WIZnet/W5100_Datasheet_v1_1_8.pdfThe data sheet is 70 pages, so I didn't read the whole thing, but searched on "state" and "MISO" and didn't see anything about tri-state.The other device is a Moteino which uses this RFM69 transceiver.https://lowpowerlab.com/shop/index.php?_route_=RFM69W&search=rfm69The link to the data sheet ishttp://www.hoperf.com/upload/rf/RFM69W-V1.3.pdfAgain, I couldn't determine anything about it's tri-state behavior.

author: Monkeh
author_rank: Super Contributor
timestamp: December 13, 2014, 09:55:51 pm
content: Quote from: scott216 on December 13, 2014, 09:41:05 pm"A transfer always starts by the NSS pin going low. MISO is high impedance when NSS is high."Page 44.READ the datasheet, don't skim it.The W5100 datasheet is indeed crap and doesn't state explicitly. It does, however, show as high impedance on the timing diagram, for what little that's worth.

author: scott216
author_rank: Regular Contributor
timestamp: December 13, 2014, 10:10:14 pm
content: Quote from: Monkeh on December 13, 2014, 09:55:51 pmThanks. I'm pretty a noob with electronics and most of the stuff on a data sheet is Greek to me, but I'm trying to learn bit by bit.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 13, 2014, 10:16:54 pm
content: You can learn a lot from taking the time to think about things in datasheets: what they're talking about, why they put them there, and what things they're bullshitting you on. The latter takes more experience to compare and contrast, but provides endless fodder for games of "datasheet bingo".Tim