TAS5760MD: THD+N & External I2S Problem

Hsieh Mingchi

Part Number: TAS5760MD
Other Parts Discussed in Thread: TAS5760XXEVM,

Hi Dear TI members,

I just trying to test TAS5760xxEVM and using the Pure Path Console Mother Board, and i just found some problems, please referred the below, thanks.

1. According to the TAS5760MD spec, at PVDD is 24V, load is 8ohm, using SW control the typical value of the THD+N is about 0.04% at 1W output, but from the "typical characteristics" waveform, the measurement result is about 0.018%, so what`s wrong about the difference? Chip variation? Or?........... So which spec can let me reference?

2. Currently, my Pure Path Console Mother Board version is F, so how to directly use the external PSIA I2S signal from the Audio Precision? Currently, the Optical and Coaxial input signal is not for using to test.

So appreciate for the answer

Best regards

over 6 years ago

0 Sadanori Kato over 6 years ago

Guru 36490 points

Hi Hsieh-san,

For Q2, please see the following information.

https://e2e.ti.com/support/amplifiers/audio_amplifiers/w/design_notes/2768.how-to-configure-ppcmb-for-external-audio-interfaces

Best regards,
Kato

0 Adam Sidelsky over 6 years ago

TI__Guru 61200 points

Hsieh-san,

Can you please provide pictures showing the two values of THD you mentioned?

I'm not seeing exactly what you are referencing.

Regards,

-Adam

0 Hsieh Mingchi over 6 years ago in reply to Sadanori Kato

Prodigy 80 points

Hi Kato San,

Thanks for your reply, so appreciate.

0 Hsieh Mingchi over 6 years ago in reply to Adam Sidelsky

Prodigy 80 points

Hi Adam San,

Please referred the attached file, from the graphic i attached, the value of the THD+N is about 0.04%, but the measurement value is about 0.018%, thanks.

0 Hsieh Mingchi over 6 years ago in reply to Adam Sidelsky

Prodigy 80 points

Hi Adam San,

Please referred the attached file, from the graphic i attached, the value of the THD+N is about 0.04%, but the measurement value is about 0.018%, thanks.

0 Alix Wan over 6 years ago

TI__Genius 9995 points

Hi Hsieh,

As to question 1, my explanation is as follows:

1. As to the table bellow, the THD+N is typcial 0.4%:

Please note that: the SPK_GAIN[1:0] = 10, so it is in hardware mode. From the table 5:

Hence, the THD+N=0.4%/typical is measured on condition that digital boost=6dB, A_GAIN=25dBV. While the figure 7 indicates that

in Software mode (EVM defaults setting: SPK_GAIN[1:0] = 11), THD+N=0.018% is measured on condition that digital boost=6dB, A_GAIN=19.2dBV(default).

In summary, the 2 different THD+N values are measured under different conditions.

2. As you known, more analog gain will amplify noise from input and digital part of our device, which can explain why THD+N @ A_GAIN=25dbV is worse than

THD+N @ 19.2dBV; In your case, you use the software mode, hence, you can ignore the values form talbe. In addition, in order to obtain better THD+N performance, I suggest you to use the gain setting as TI suggested in our datasheet.

Thanks & best regards,

Alix Wan

Audio

Audio forum

TAS5760MD: THD+N & External I2S Problem