Spot the datasheet error - Page 1
Forum section: electronics / projects

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 31, 2013, 01:55:32 am
content: This schematic is an application from the TLC3702 datasheet. The TLC3702 is a dual comparator with push-pull outputs.There is an error that prevents the circuit from working as intended. Can you spot the error?

author: Rufus
author_rank: Super Contributor
timestamp: May 31, 2013, 02:13:03 am
content: Quote from: TerminalJack505 on May 31, 2013, 01:55:32 amIt depends what the prizes are....

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 31, 2013, 02:15:14 am
content: The prize for the first correct answer is:Bragging Rights!Does a nerd need anything more?

author: Rufus
author_rank: Super Contributor
timestamp: May 31, 2013, 02:21:05 am
content: Quote from: TerminalJack505 on May 31, 2013, 02:15:14 amI'll pass. It is just a dumb mistake. I would criticize it more for crappy arrangement of the oscillator components.

author: smashedProton
author_rank: Frequent Contributor
timestamp: May 31, 2013, 05:42:27 am
content: Please don't make fun of me if I'm wrong... I'm a beginner.The input signal is going into the wrong terminal on the left. It should be on the positive

author: smashedProton
author_rank: Frequent Contributor
timestamp: May 31, 2013, 05:43:59 am
content: Oh,both drive amps are coherent.

author: smashedProton
author_rank: Frequent Contributor
timestamp: May 31, 2013, 05:46:46 am
content: Nope... what is the error?

author: c4757p
author_rank: Super Contributor
timestamp: May 31, 2013, 05:50:46 am
content: Ooh! Ooh! I know! Pick me!They let monkeys draw the left half of the schematic!(C'mon, it's an easy one. Look closely. Attention to detail, people!)Quote from: smashedProton on May 31, 2013, 05:43:59 amDifferent part numbers; I'd assume one responds inversely. (Couldn't find a datasheet to confirm.) That isn't wrong.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 31, 2013, 05:52:03 am
content: Quote from: smashedProton on May 31, 2013, 05:42:27 amCorrect. Yay! Bragging rights go to smashedProton.Don't worry. I didn't spot it right away. In fact I have the part and was going to build an oscillator with it and noticed the one in the datasheet so I tried to simulate it and it didn't work. Ithenbuilt it on a breadboard and it still didn't work.I guess I just put too much trust in the guys writing and proof-reading the datasheet. You would think they would know their stuff.

author: c4757p
author_rank: Super Contributor
timestamp: May 31, 2013, 05:54:20 am
content: Now wait just a gosh darned minute. I want bragging rights too."1/2 TLC3704"? I don't think so... TLC3702!

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 31, 2013, 05:54:43 am
content: Quote from: c4757p on May 31, 2013, 05:50:46 amYou get a runner's-up prize for spotting the different part numbers. Not sure what happened there.

author: c4757p
author_rank: Super Contributor
timestamp: May 31, 2013, 05:59:26 am
content: That's not even what I was talking about in that quote! I meant the SN75603/4 - spent quite a while looking for the datasheet for that... Still didn't find one - but I assume one is inverting.They really ought to update those datasheets with a different part. The only references to that chip I could turn up, besides a few people selling them with no description of what they are, were in TI comparator datasheets... They've got to have another motor driver in their extensive catalog!

author: HackedFridgeMagnet
author_rank: Super Contributor
timestamp: May 31, 2013, 06:37:30 am
content: I don't really know but I am guessing the LHS doesn't oscillate.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 31, 2013, 06:59:18 am
content: Quote from: HackedFridgeMagnet on May 31, 2013, 06:37:30 amYes, that's correct. The two inputs are swapped and the comparator won't oscillate. The oscillator portion of the schematic should look more something like the attached schematic.