Simple audio jack detect IC with load switch - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: March 26, 2021, 07:41:47 pm
content: Hi,I have been looking everywhere for a integrated IC that detects an audio jack is inserted (through the Detect pin of a common jack socket) and enables a load switch (up to 400mA).But haven't found any.Does anybody have any suggestion for part?Thank you

author: Zero999
author_rank: Super Contributor
timestamp: March 26, 2021, 09:52:49 pm
content: A relay?

author: Buriedcode
author_rank: Super Contributor
timestamp: March 26, 2021, 10:00:19 pm
content: Quote from: ricko_uk on March 26, 2021, 07:41:47 pmMaybe a USB load switch? I mean the fact its for an audio jack means nothing

author: tooki
author_rank: Super Contributor
timestamp: March 27, 2021, 01:29:49 pm
content: Quote from: ricko_uk on March 26, 2021, 07:41:47 pmBear in mind that most audio jack switches aren’t isolated from the audio signal, making them fairly difficult to use with simple logic. For an audio project where I wanted to have insertion detection, I simply chose a jack with an isolated switch. That made it easy to read using the MCU.(In my case, I found a jack withthreeswitches: the isolated switch, plus one break-on-insert switch on each stereo channel. This makes it easy to avoid having the inputs floating, which was a design requirement. The nonmoving contacts are grounded, pulling the input to ground, but upon insertion those get disconnected.)

author: ricko_uk
author_rank: Super Contributor
timestamp: March 27, 2021, 07:01:37 pm
content: Thank you all,the issue is what Tooki mentioned. Detecting the insertion through the break-on-insert of the jack. There are plenty of switching solutions but what I am looking for is an integrated solution that detects the break-on-insert of the audio jack.Preferably with a load switch, but if not at least the break-on-insert of the jackwithout affecting the audio signal.Thank you

author: Zero999
author_rank: Super Contributor
timestamp: March 27, 2021, 07:32:04 pm
content: What sort of audio jack is it? There are different types. Refer to the article linked below. I was hoping for more information to enable me to better answer the question.https://www.cuidevices.com/blog/understanding-audio-jack-switches-and-schematics

author: ricko_uk
author_rank: Super Contributor
timestamp: March 28, 2021, 01:26:39 am
content: Thank you Zero999,there are two types for two different version of the product.The first is a 3.5mm stereo socket with two detect pins, one on each of the channels (left and right) like in the first attached picture (green connections).The second is still a 3.5mm stereo but is a 6-pins socket for a 4-contacts jack. We only use stereo so it looks like when the jack is inserted the sleeve and ring 2 (see B&W picture) all short together. Also it looks like 4 and 6 both make (instead of break) when the jack is inserted.Thank you

author: tooki
author_rank: Super Contributor
timestamp: March 28, 2021, 11:34:59 am
content: Quote from: ricko_uk on March 28, 2021, 01:26:39 amIn a 4-pin plug, as used in most cellphone headsets, the sleeve is the microphone input, ring 2 is ground, ring 1 is R, and tip is L. With the jack shown, if a stereo plug is inserted, sleeve and the two ring 2 contacts all short to ground. But if a headset is inserted, only ring 2 gets shorted.The idea with the shorting contacts on ground is that one side is always on ground, while the other is connected to logic input, with a pull-up resistor. When inserted, the input side is shorted to ground, pulling it low and allowing the MCU to detect it.Anyhow, I’m a bit baffled by your search for a supposed dedicated solution. Typically, the insertion detect circuits are built into audio chips of various types (like codecs, DACs, headphone amps, and Bluetooth audio ICs. So that’s where you’d add it, not to the load switch circuit, since a load switch as such isn’t a typical part of such a device.As for the stereo jack you show, let’s be clear: the switches in it aren’t intended as “detect pins”, they’re the classic design used to mechanically disconnect built-in speakers when a plug is inserted. The control circuitry doesn’t know or care whether it’s inserted or not.Your question sounds to me like a classic XY problem, where the asker is asking for help for a solution that is inherently unsound, rather than explaining the root problem and accepting more holistic solutions.

author: ricko_uk
author_rank: Super Contributor
timestamp: March 28, 2021, 04:35:22 pm
content: Thank you Tooki for the explanation,ref the XY problem, what I mentioned in the OP is all there is to it. Just enable a load switch. The rest of the circuit on the tiny PCB is just a couple of op-amp current sources that follow the audio signal coming in.The idea is that the circuit does not consume any power is there is no jack inserted.Once I complete the schematic and I will post it here.Thank you

author: tooki
author_rank: Super Contributor
timestamp: March 28, 2021, 04:51:55 pm
content: Then you could either use the ground-shorting jack as shown in the second jack, or use a jack with an isolated switch, to control a simple MOSFET switch to connect power.

author: Jan Audio
author_rank: Frequent Contributor
timestamp: March 29, 2021, 02:22:24 pm
content: Quote from: ricko_uk on March 28, 2021, 04:35:22 pmYou mean when there is no audio playing.btw : whats wrong with a switch or button.

author: ricko_uk
author_rank: Super Contributor
timestamp: March 29, 2021, 11:46:53 pm
content: Thank you Jan and Tooki,Jan,at the moment the idea is "when the jack is not plugged in" but if extremely simple to implement having it to turn off when where is no audio playing is also a possibility. How would I do that in a reliable way?There is no space for any switch and even if there was the usability of the product requires no switches.Tooki,we have to use two specific jacks which have the connections shown in the earlier posts pictures. So the isolated switch would be nice but not an option.

author: tooki
author_rank: Super Contributor
timestamp: March 30, 2021, 05:55:05 am
content: In that case, you’re looking for not only one non-existent part, but two totally different ones, since you can’t really use the same plug detect method on both of those jacks.What you could do, then, is not detect theplug, but theinput signal. This is commonly done in active speakers. If the jacks are for audio output, it’d get a lot harder, since detecting a load is trickier. Earphones might not be too hard, but a high-impedance load like an amp might be very hard to detect.Again, XY problem...