PCM6260-Q1: question about the ADC results difference between differential input and single-ended input

Iris Shen

Part Number: PCM6260-Q1

Hi team,

For PCM6260-Q1, for example, single-ended input amplitude is V=2V, differential input amplitude is V=1V, so actual input voltage=(V+) - (V-)=2V.

From our understanding, the ADC conversion results should be the same for single-ended and differential input. But the test results show single-ended is 6dB more than differential.

Is there any like internal gain setting difference? Could you please help to explain the reason?

over 2 years ago

0 Sanjay Dixit over 2 years ago

TI__Mastermind 23030 points

5V rms single ended signal gives 0dbFS or full scale value

10Vrms differential signal gives 0dbFS or full scale value

Both are when channel gain is 0db.

A 5V rms signal is 14Vpp . This is about the maximum signal level that can be electrically applied to the pin and when in single ended mode it results in full scale value .

A 10V rms differential signal means 5V rms on each pin. This translates to 14Vpp on the pin.

There is an internal scaling that gives 0dBFS at this differential scaling

0 Iris Shen over 2 years ago in reply to Sanjay Dixit

TI__Expert 4002 points

Hi Sanjay,

Thanks for your answer but I am a litter confused. Did you understand my question?

I mean the channel gain settings are the same, but for example, a 10V rms differential signal and a 5V rms single ended signal, are the ADC conversion results expected to be the same？

+1 Jeff McPherson over 2 years ago in reply to Iris Shen

TI__Guru 50250 points

Hi Iris,

What you are seeing is expected. You are giving 2Vrms in both single ended and differential point of view. Because the differential scale is double that of the single ended scale, that is where the 6dB difference is coming from.

Best regards,
Jeff McPherson

0 Iris Shen over 2 years ago in reply to Jeff McPherson

TI__Expert 4002 points

Hi Jeff,

Understood and thanks!

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PCM6260-Q1: question about the ADC results difference between differential input and single-ended input