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BQ24133 white noise to audio lines

Brian Han
Intellectual 330 points
Other Parts Discussed in Thread: TLV320AIC3204, TPA3110D2, BQ24133, LM3481

Hello,

I'm making a portable Bluetooth speaker using TI BQ24133 PMIC, TLV320AIC3204 codec, TPA3110d2 AMP.

I was successful with the board bring up, but there are some serious noises(white noise + power noise) going into the audio line whenever BQ24133 is powered up.

I added a schematics of my circuit below. I mostly referenced the datasheet's example circuit and portable boombox example in this page"http://www.ti.com/tool/pmp9491?keyMatch=portable%20speaker&tisearch=Search-EN-Everything"

System condition is.

12V, 2A DC power input through VIN

7.4V 2s1p Li-ion battery connected to BAT +

Using Nominal 7W,  Max 20W speakers. LM3481 DCDC boost up powers the TPA3110d2.

I'm not sure if the power is directly affecting the audio lines or it's some kind of parasitic noise.

I'm thinking of adding a LC filter in between the codec and the class D amp and see if it filter out the white noise

But is there anything wrong with my schematic that is causing this mess?

Thank You

  • 0
    TI__Genius 11480 points

    Hi Brian,

    The noise is most likely coming from radiated EMI. If this is the case, it will be layout related. It sounds like you have a lot of switching sub-circuits, which means you have to be very careful with your layout.

    A couple things:

    • Make sure the SW or PH node is as small as physically possible in your layout.
    • Be careful with large di/dt loops. These current loops are usually through the low side fet, inductor, and output cap and connected through ground. This means you want the grounds of these components to be close together in your layout.
    • You can isolate noise sensitive lines by adding a ground plane (between layers) or a "dummy trace" around noise sensitive lines (for noise coming from the same layer). 

    You can definitely try to add a filter to get rid of the noise, but the root cause is most likely with layout.

    If you'd like, I can review your layout for you. My email is d-wiest@ti.com if you are not comfortable putting it here.