TAS5825M: TAS5825M Inductive whistling problem

hi Pan

usually, the whistling is not caused by inductor, only capacitor has this kind of whistling.

as capacitor's has 2 conductive plates, this plates vibrating can generate sound.

using smaller size capacitor might soften this problem. but sometimes, it cannot be avoided.

thanks

jesse

Dear Jesse

I tried the same capacitor on the male board and there was no significant improvement, we listened to it and still think the sound is coming from the inductor, please help me to see if there is any other solution to the problem, attached is a picture of the parameters of the inductor we are using

hi Pan

maybe below several actions might be helpful to you.

1. play single tone, check which frequency can lead the noise be louder. if do have some frequency affect the sound, you can do some suppressing at the frequency.

2. as i cannot find the ds of your inductor, you can take a try several kind of inductor to see whether this can be soften.

-inductor with large DCR, we can see if the ripple at pwm be soften or not, not sure whether this can help this issue.

-inductor with large inductance, this can filter more high frequency, this might help this case.

-capacitor with large capacitance, this is also for filtering more high frequency, this might help this case.

-above "same capacitor", you mean small size cap? have you tried smaller size capacitor?

tkx

jesse

Dear Jesse

Would an NPO or COG type capacitor improve the noise?

hi Pan

i am sorry that we don't have related study for this 2 types of cap.

maybe you can confirm with cap manufacture for more information.

tks

jesse

Dear  Jesse

We have tried the smaller size MLCC , change from 0805 to 0603,but the improvement in reducing the noise (whistling) is minimal. Can we try using MLCC capacitors with an even smaller 0402 package? If the smaller MLCCs still do not bring improvement, can we try using electrolytic capacitors with a smaller package? Will this have any impact on the power amplifier output?

Our current circuit design is as shown in the figure below. Are there any other suggestions for improvement?

hi Pan

pls refer below comment:

1.0402 can be used. but as the capacitance error might be large as the size is small. maybe try 1uF is better.

2.Electrolytic capacitor is not recommended. it is usually be used for DC voltage like connecting with PVDD as bypass cap.

tks

jesse

Hi Jesse

I have tried the 0402 1μF capacitor, but it didn't produce any obvious effect. Could you please provide any other suggestions?

Hi，Jesse

Our current usage scenario involves two speakers with a maximum specification of 20W/8 ohms, and in practice, their output will be limited to 10W. Is there any issue with our current hardware design under this scenario?

can we change the AC12 ,AC21,AC25,AC31 from 680nF to 100nF  or 220nF,is there any risk for this change

hi Pan

no problem using above cap.

220nF is recommended. 100nF might affect the FR at high frequency.

thanks

jesse

HI Jesse,

How can we Reduce the output power to 10W ,The Speaker is 4Ohm 10W