TAS5731M: Output level at 0 dB Volume

Akio Ito

Part Number: TAS5731M
Other Parts Discussed in Thread: TAS5731

Hi,

When Biquad filter, DRC, Mixer and Volume register gain settings are all 0dB and input signal level is 0dBFS, does TAS5731M output full scale with non-clipping?

Best regards,

Akio Ito

over 5 years ago

0 Matthew Miao over 5 years ago

TI__Expert 6720 points

Hi Akio,

No clipping from the digital side. However, the analog (PVDD) clipping is related to PVDD value and output sinewave amplitude.

Rdgs,
Matthew

0 Akio Ito over 5 years ago in reply to Matthew Miao

Genius 3595 points

Matthew-san,

TAS5731M is an open loop device, isn't it?
The output level of open loop devices may be decided by PVDD and duty cycle of PWM.
I think that volume register value is not related with PVDD.

Best regards,
Akio Ito

0 Matthew Miao over 5 years ago in reply to Akio Ito

TI__Expert 6720 points

Hi Akio,

You are correct. TAS5731 is an open loop device, which generates PWM duty cycle not fixed gain output. So the analog gain is related to PVDD value.

Then regarding the 0dBFS input, there is no clipping in the whole signal path. Did you see any unexpected behavior?

Rdgs,
Matthew

0 Akio Ito over 5 years ago in reply to Matthew Miao

Genius 3595 points

Matthew-san,

We don't have the EVM, and our customer doesn't have too. So, I posted this question.

Best regard,
Akio

0 Xiaolin Qin over 4 years ago in reply to Akio Ito

TI__Expert 6295 points

will you share PVDD and analog gain setting for us to help further proposal about clipping?

Regards
Linda

0 Akio Ito over 4 years ago in reply to Xiaolin Qin

Genius 3595 points

Linda-san,

I'm sorry for the late my reply because of long holiday.
PVDD etc. are TBD.
As I got a TS5731MEVM, I measured THD+N vs Amplitude and waveform as shown below.

He understood that PWM output was full scaled at 0dB volume by these measurement results.
But he asks why THD+N increases before clipping.
Can you tell us the reasons?

Best regards,

Akio Ito

0 Matthew Miao over 4 years ago in reply to Akio Ito

TI__Expert 6720 points

Hi Akio,

what's your output configuration and speaker connection? TAS5731 GDE default configuration is 2.0 mode as below.

Then you need to connect load to BTL AB or BTL CD:

Rdgs,

Matthew

0 Akio Ito over 4 years ago in reply to Matthew Miao

Genius 3595 points

Matthew-san,

I measured TAS5731M with mode_2_0 setting. The evidence of BTL operation is the amplitude of WAVEFORM exceeds 20 Vp-p.

In the case of a class AB amplifier, THD degrades as the amplitude increases due to the non-linearity of the input versus output characteristics.
Our customer's question is why THD degrades with large amplitude in spite of using digital PWM with noise shaper.

Best regards,

Akio Ito

0 Xiaolin Qin over 4 years ago in reply to Akio Ito

TI__Expert 6295 points

hello Akio,

did you monitor noise as well? by the way, you may need give detailed GDE setting and register configuration, PVDD, Load for Matthew, so he can help you further analysis.

Regards
Linda