TAS5548 EVM headphone DC output

Panson Poon

Intellectual 420 points

Other Parts Discussed in Thread: TAS5548

I found my TAS5548 headphone output DC on both L and R channels. How can I remove it?

over 11 years ago

0 user5276421 over 11 years ago

TI__Mastermind 37045 points

Hi Panson,

Is the DC offset due to the low pass filter for the headphone output? Are you using the EVM? What is the magnitude of the DC offset? Can you use DC blocking caps?

reg,

Paul.

0 Panson Poon over 11 years ago in reply to user5276421

Intellectual 420 points

Hi Paul,

Yes, this is TI TAS5548 EVM. The DC offset is ~1.2V each channel. Is it normal to see such a high DC offset? The input PWM is not DC balanced?

I can add a DC blocking cap. But this is a bit surprised!

Cheers,

Panson

0 user5276421 over 11 years ago in reply to Panson Poon

TI__Mastermind 37045 points

Hi, Panson,

I think the DC offset it likely due to the external components mismatch and DC offset of the HP amp.

Try adding a 30K ohms resistor at C34 to gnd to mirror the R34 resistor. Do the same for C35 cap. See if this helps.

reg,

Paul.

0 Panson Poon over 11 years ago in reply to user5276421

Intellectual 420 points

Hi Paul,

Yes, the mod solved the problem. Thanks!

My impression is that the EVM was not well tested before released to market. Such DC output was neither due to mismatch nor opamp offset, but an incomplete circuit.

Cheers,

Panson

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TAS5548 EVM headphone DC output