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TAS5548: How can measure the device output to get the PWM Processing THD+N < 0.1% (0–40 kHz)?

JIM WANG
Prodigy 200 points
Part Number: TAS5548


Hi,

Could you provide some help on TAS5548 8-Channel HD Compatible Audio Processor with ASRC and PWM Output ？

According to it datasheet, it claims PWM Processing – THD+N < 0.1% (0–40 kHz) on Page 1.

And in section 6.6 dynamic performance, it claims 

Total harmonic distortion TAS5548 output (1kHz at -1dBFS) 0.01%


Can I know under what test condition e.g. what kind of test circuit is used to get the THD result?

THANKS,

JIM.

  • 0
    TI__Guru 65650 points
    Jim,

    We have a custom board here used for evaluation and characterization. It converts the PWM output back to analog without adding measurable distortion and the device is characterized that way.

    Regards,

    -Adam
  • 0 in reply to Adam Sidelsky
    Prodigy 200 points

    Hi Adam,

    Thanks for your reply. We tried to feed the PWM signal into our test circuit but it has relatively high distortion (1.5%).

     

    Can you provide some information on the evaluation custom board that you used for the THD testing?

     

    Or can I have the SCH by any chance?

     

    Thanks and best regards,

    Jim.

  • 0 in reply to JIM WANG
    TI__Guru 65650 points

    Jim,

    Since we closed this via email, I will summarize here.

    Our circuit is simply a buffer after each TAS5548 output which is then fed into a differential op-amp active low-pass filter. The OUT1+ and OUT1- are the differential inputs to the op-amp and the output is fed to an XLR which can then be cabled to a AUX-0025 and Analog Precision Analyzer. This is repeated for all TAS5548 outputs.

    Regards,

    -Adam


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