Digital Isolator vs Optocoupler? - Page 1
Forum section: electronics / beginners

author: ftransform
author_rank: Frequent Contributor
timestamp: March 24, 2013, 02:53:42 am
content: So I ordered a digital isolator, not really considering how it works, and when I read the datasheet to my alarm I found out that it uses radio signals to transmit information.Since I want to use it to communicate serial from a ADC I got paranoid about it being a noise source.I found one mention of this potential problem on dangerousprototypes.com but I cannot find information on google.To me it seems that putting a radio frequency transmitter right next to my ADC is a big no no, or are these devices nice and quiet? Since it was not mentioned in the datasheet (for instance analog devices icoupler system) to be low noise I expect it to be a problem.Has anyone here used these devices next to a sensitive ADC and determined if they are detrimental?Lesson learned to very carefully read the datasheet before purchasingI am about to jury rig some bullshit out of shrink tubing, photodiodes and LED's because I am brokeI got this thinghttp://www.digikey.com.au/product-detail/en/SI8431AB-D-IS/336-1758-5-ND/2170665Is it worth pursuing a optical method?

author: digsys
author_rank: Unknown
timestamp: March 24, 2013, 04:55:10 am
content: The Silabs isolators are one of the best around. I use many 100s, in many designs. There is NO, or negligible spuriousradiation emission, and I've never heard of an issue near adc's. IF you want to be extra-certain, put 10/100pF ceramiccaps right at the inputs. No need to panic :-)Edit: The advantages are WELL worth it as well.

author: ftransform
author_rank: Frequent Contributor
timestamp: March 24, 2013, 04:58:18 am
content: Quote from: digsys on March 24, 2013, 04:55:10 amGood to know I was ripping my hair out looking for a cheap optical solution.I wish they would advertize that fact better. It looks like a discrete optical solution for 6 lines would cost me 30$+, so I am very happy to get away with 5$.I will also put some ferrite on the power rail for it.

author: andete
author_rank: Contributor
timestamp: March 24, 2013, 06:14:20 am
content: Very interesting, as a newbie, I didn't even knew these digital isolators exist.The link mentioned in the original post:http://www.digikey.com.au/product-detail/en/SI8431AB-D-IS/336-1758-5-ND/2170665actually contains a hyperlink namedDigital Isolators vs. Optocouplersthat has a video showing the basics of the device.

author: digsys
author_rank: Unknown
timestamp: March 24, 2013, 10:31:54 am
content: For the price, they're pretty awesome. 1 / 10MHz transfer, ultra-low jitter/skew, pretty much fixed 1.6mA over the range.Perfect for SPI, SCI, CAN, USB etc

author: knarf.be
author_rank: Contributor
timestamp: March 24, 2013, 08:53:02 pm
content: A good advice: always sleep a night over every decision, mostly you won't regret it!Yesterday I wanted to buy a DMM from a local store, but it costed € 100, so I slept a night over it, and today I found a DMM well better than the € 100 (true RMS) for € 50 here on the forum.Always sleep a night over something when you have the time

author: ftransform
author_rank: Frequent Contributor
timestamp: March 24, 2013, 11:36:46 pm
content: Quote from: knarf.be on March 24, 2013, 08:53:02 pmThen this project would take 3 billion years

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 25, 2013, 12:06:22 am
content: NVEAlso do a big range of digital isolators, includingthese neat oneswith passive inputs

author: c4757p
author_rank: Super Contributor
timestamp: March 25, 2013, 12:21:33 am
content: Quote from: mikeselectricstuff on March 25, 2013, 12:06:22 amThose are pretty cool.