Hi I am using a bluetooth module and giving output of it via differential to single ended using TPA6138 and it output given to audio output via aux or RCA analog. And I am having a tick tick sound when we hit advertising mode on the Module.
Advertising mode is like discoverable mode. It is like getting motorboat sound and surprisingly it is synchronizing with the LED's. I also have turned off the LED's by giving LED turn off command. Still I hear the tick tick sound. I guess it is in the ground because of ground isolation. How do we get the noise off the ground loop. Or is it the module creating the noise. It is actually a high frequency noise from the output of the bluetooth module the differential output.
TIP: I guess the sound is in the ground. I have analog and digital ground separated via 0ohm. I replaced it with ferrite bead it reduced it very lightly. Its random high frequency sound which is not going. Any advice would be appreciated. I tried a lot like taking the output audio running it via LOW pass filter also tried a second order band pass nothing worked.
Depending on circuitry or what is possible.... they try to have all grounds connected to one point. Or can use isolation transformers.... or balanced inputs and balanced output. The high frequency blocker was a good idea too obviously.
Good shielding if possible. And maybe consideration of cables and coils and orientation with respect to noise sources....to avoid magnetic coupling. Ensure good ground connections and ground conductors to minimise noise voltage across ground cables.
Or noise suppression at the source if possible.
Show us your schematic, so we do not have to guess about what you're doing.
Yes it is in my other laptop. Will upload soon. The thing is when I connect analog ground of the class D amp module with Analog ground of the bluetooth module. The noise suppresses but still there very low. Also, When connecting to earth ground it reduces but not completely. Ferrite bead with 120ohm also reducing it. I want to completely eliminate it. It might be the noise in the ground. Its basically high frequency noise.
It appears that what you're experiencing is actually called motor boating. It's actually a parasitic oscillation of a few Hertz that sounds like an outboard engine idling, and was quite common back in the day of chassis mount equipment predating PCB solid state.
The feedback sustaining the oscillations is usually being derived from one or more sources often as a result of poor or improper configuration/assembly such as flying leads on a breadboard prototype or long or improper ground run(s) on a PCB to multiple common points for just two common examples.
The exact cause of these oscillations can be very simple or very complex in nature. Proper design of a given circuit layout is the first step to avoiding the issue. Implementation of certain practices and techniques such a Star grounding, proper decouplingand shielding when necessary go a long way toward preventing parasitic feedback generation and paths.
Yes I think its the same. But what are the methods now to eliminate it without doing any design change.
Like any use of ground loop isolators or ferrite bead or something. Its the noise coming out from the module. Does the placing of Bluetooth module place a crucial role ? As I placed no copper layer no analog ground templates under the antennae portion of the module.
Probably best to include a block diagram of systems involved.... bluetooth model brand etc. Basic circuit and connections. Otherwise it could become a wild goose chase due to misunderstanding and lack of details about the systems involved.
ajaydillikar:
Yes I think its the same. But what are the methods now to eliminate it without doing any design change.
Anything you do from this point is a design change to correct a defect of the initial design. But those changes should be performed from the perspective of informed diagnosis of a problem and not guess work. That is troubleshooting 101.
ajaydillikar:
Like any use of ground loop isolators or ferrite bead or something.
It's possible that could be a consideration, but is there evidence that either of those impact the feedback path in phase and amplitude to eliminate the issue? That is the aim to rid your design of that parasitic oscillation.
ajaydillikar:
Its the noise coming out from the module.
Are you certain of that? What test equipment did you use to discover that to isolate the problem to that? Are you certain that the module isn't just one of the links in the feedback loop?
ajaydillikar:
Does the placing of Bluetooth module place a crucial role ?
It may or may not. The only way you can be helped at this point with a possible diagnosis of the motor boating issue is to supply a detailed schematic of your design; not a block diagram or a quick sketch but a true schematic of the as built device. Also, the PCB layouts including ALL layers (screen shots) of ANY & ALL boards laid out for the design including any ground or power planes. Also, pictures can be worth a thousand words.
ajaydillikar:
As I placed no copper layer no analog ground templates under the antennae portion of the module.
Ground and power planes are your friends to avoid this very type of issue. Did you include any ground plane in your board layout?
Hey, I'm not trying to break your back for some power trip, but the problem you have encountered is one of toughest to correct long distance without a butt ton of information. Also, I've gone through this drill with many a student in the past. Just remember that most problems have a solution except perhaps entropy!
I look forward to your information to help with finding a solution for you. Cheers!
Attached is one bluetooth board schematic. Other birch which attaches to it is just an output connectors with analog and digital ground connected via 0ohm resistor.
I was happy using 120ohm ferrite bead reducing the noise. So was thinking of using lower values of ferrite bead. I think the noise is some what closer to bluetooth antennae and around 2.4mhz. Yes i have analog ground plane on both top and bottom layers. Also, I have left a space small around antennae region with no ground plane as was suggested in the data sheet.
Below is the link of the module i used: Click under documents to go to dat sheet and many other documents:
https://www.bluecreation.com/product_info.php?products_id=38
2 didoes anti-parallel to eatch other, bypasse with a 5 ohm 10 watt resistor should do the trick?
ajaydillikar:
2 didoes anti-parallel to eatch other, bypasse with a 5 ohm 10 watt resistor should do the trick?
Go for it, and have a nice Easter!