LC filter for TAS5731M

Fai Chan

Other Parts Discussed in Thread: TAS5731M

Hi TI experts

Currently, I am using TAS5731M for BTL & PBTL mode. And I noticed that I need to add LC filter before connect to speaker drivers.

My questions :

1) Does the LC filter use to filter out the PWM switching rate ?

2) So if I am using 48K as the sampling rate, then I need to filter out PWM switching rate at 384K?

3) How do I calculate the accurate value of the LC filters for TAS5731M ? Do you have any design guide for it ?

Thank you

Fai

over 7 years ago

0 Diego Melendez over 7 years ago

TI__Guru 57800 points

Hi, Fai,

Yes, the LC filter is used to filter the high frequency content that comes form the PWM carrier signal in the output of the Class-D amplifier. Generally, it is recommended to design the filter to cutoff frequencies higher than the audible specter. Please refer to the SLOA119B application note, there you can find detailed information about LC

Best Regards,

-Diego Meléndez López
Audio Applications Engineer

0 Fai Chan over 7 years ago in reply to Diego Melendez

Intellectual 440 points

Hi Diego,

Got it. Thank you

Fai

0 Fai Chan over 7 years ago in reply to Diego Melendez

Intellectual 440 points

Hi Diego,

What If I use a Low Pass Filter in TAS5731M's EQ , do I still need the external LC filter circuit to filter the high frequency from the PWM carrier ?

Thank you
Fai

0 Diego Melendez over 7 years ago in reply to Fai Chan

TI__Guru 57800 points

Hi, Fai,

Even if a low pass filter is configured in the EQ of the amplifier, the LC Filter is required as the Class-D amplifier output is a PWM. The effect of the low pass filter in the Audio processing of the amplifier will affect only the audio signal, not the output PWM carrier.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer

0 Fai Chan over 7 years ago in reply to Diego Melendez

Intellectual 440 points

Hi Diego,

Got it, Thank you

Fai

Audio

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LC filter for TAS5731M