TPA2006D1: Noise in Amplifier output with no audio input

Hi Kiran,

Does removing the inductor eliminates the noise?
Could you share the connections of the output of the amplifier? Perhaps you could change the common-mode inductor for a ferrite-bead/capacitor filter.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

I'm kiran's colleague. Removing the inductor did not eliminate the noise.

We tried different combinations of ferrite-bead/capacitor filter, but couldn't find a positive outcome.

Attached the schematics for your reference. (note: Interchanging R108 & C75 did not make any difference in the noise level).

Please let us know ways to eliminate this noise.

Regards,

Gireesh

Hi Gireesh,

Do you have captures of the inputs?
Could you try to short both inputs to GND? Or just short both inputs between them (not to GND)? This way the output should be affected only by the amp.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

We tested by shorting both inputs of amplifier to ground, we could see a noise reduced to a great extend.

Could you let us know what value of RC should be use to allow a good amount filtering when inputs are connected.

  Current values are R=20.5KOhm C =3.3nF.

Thanks & Regards,

Kiran

Kiran,

I just noticed that the label of the input to TPA2006D1 is called "codec", so am I right to assume this is the output from a DAC?
If that's the case, I would recommend to add an RC Low-Pass Filter before the DC coupling input capacitor and the input resistor. Calculate the value of the LPF components to that the cutoff frequency is around 22kHz, in case you're using the whole audio bandwidth.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Kiran,

Have you tried with the LPF filter as mentioned above?
Are there still any questions?

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators

Hi Ivan,

We tried placing LPF as you have mentioned, below are the details of the same. But we couldn't find a significant reduction in the noise by using this LPF. Please review the LPF circuitry we have used and let us know if we need to modify anything.

LPF:

RC filter: R=1K , C=6.8nF , Cutoff Frequency=23.4Khz

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Regards,
Gireesh

Gireesh,

By shorting the inputs the noise was reduced, as you tested before. So the noise is not being caused by the amp itself, you should inspect your system to look for the source of the noise.
That jitter at the output could be caused by noise at the input or perhaps at VDD source voltage.

Best regards,
-Ivan Salazar
Applications Engineer - Low Power Audio & Actuators