Filter inductance of ma12070p power amplifier chip

[jacksl528]

Hello, engineer
I used three ma12070ps to make a multichannel power amplifier,
After power on, the chip can work normally, but why does the output low-pass filter inductor (6.8uh) make a "Zizi" sound

What causes the inductive filter to make physical noise?? Thank you

[Pranava_YN]

Hey,

Can you please let me know the maximum operating frequency of the amplifier. Also let me know if the sound still exist even when you vary the cutoff frequency of the output filter.

[jacksl528 · Accepted solution]

Hello! Pranava

Sorry, I don't know how to set the working frequency of the chip. I use the default circuit diagram.

[jacksl528]

Thank you for your reply

[jacksl528]

If I change the inductance from 6.8uh to 10uh, the squeaking noise will be reduced.

This sound is not from the horn, but from the inductor itself

[Pranava_YN]

Hi,

You can take a look at this KBA. https://community.infineon.com/t5/Knowledge-Base-Articles/Reduce-Audible-Noise-from-SMPS-Inductor-KB...

Even though most of it is regarding SMPS, the cause of the noise is the frequency component. Please check few solutions mentioned at the end of that article.

[jacksl528]

Thank you for your reply

[Audio-guru-CPH]

Hello jacksl528.

Sometimes unfortunate combinations of filter values and physical layout can cause audible SPL noise. It is caused by out-of-band noise just above the audio spectrum (+20kHz, generated by the switching nature of the amplifier) causing intermodulation products in the inductors/ PCB trace stray capacities. This noise can be limited by using PMP1 or PM2 and lowering the inductance of the inductors. Using inductors with higher saturation current capabilities or using ferrite beads can also remedy this. PCB layout should follow that from the MA12070P EVK. Please see https://www.infineon.com/dgdl/Infineon-UserManual_ClassD_audio_MERUS_evaluation_boards-ApplicationNo...

Best regards,

Rasmus.