TLV320AIC3104: White Noise problem

Hi,

-. It's hard to say what causes that, are you seeing this on several units or just one setup? The SNR spec is with 0dB setting on all control in the path. Maybe use AP and measure the SNR for this unit.

-. Noise could come from anywhere, but here is an apps. note that talks about noise in audio. 

https://www.ti.com/lit/an/slaa749/slaa749.pdf?ts=1694723618295&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTLV320AIC3104

Have you tried in your case, reduce volume in R43 and gain up in R89?

-. This is referring to record path shown below, in this case DAC must be powered down. ADC processing is referred to the ADC path/block - the decimation etc....

In order to use this recording path, playback will not be enabled.

Regards

read_reg.zip

Dear TI Support Team.

For this issue(White noise from DAC_L1(R89), I'm attaching the reg value for our product when it happens.

So far, according to our testing, the white noise source is DAC_L1(R89) .

If I do mute R43 in the previous register, I can hear the white noise.

In our app, DAC_L1 is used for a melody ring play from CPU.

This DAC_L1 is mixing for Right LOP/M with PGA_L(R88). 

The PGA_L(R88) is connected to R15 PGA / MICx by bypassing ADC and 3D processing block. This is used for voice path.

So the melody ring or voice can be played on Right LO .

Under this condition, If we disconnect or mute DAC_L1(R89), white noise is disappear. 

Seemingly, the issue seems to be DAC_L1(R89) itself. (Currently 0dB setting)

The white noise is not a specific narrow band sound. It's pure white noise.

In a case, when I tried to do below, the noise is disappeared.

1. powered down - DAC_L1(R37.7) 

2. Set  volumes, gains in that audio path.

3. Route DAC_L1(R89.7)

4. Set Volume - DAC_L1(R89.6:0)

5.powered up DAC_L1(R37.7).

--> I can't hear the white noise in this case. However, this way is always not effective in every voice path case.

And the noise level is depending on R109 (0--> 50% -->100% is more loud).

Currently we are using DAC_L1(R89, 0dB) , Right LO(R93, +1dB). for the melody ring path

Decreasing R89 and increasing R93 are another option to improve the white noise. But I'd like to improve DAC_L1 noise first.

Please advise me about this issue

This is our audio block.

Best regards

Byunghee Sohn

6012.read_reg.zip

Dear TI Support Team.

For this issue(White noise from DAC_L1(R89), I'm attaching the reg value(read_reg.zip) for our product when it happens.

So far, according to our testing, the white noise source is DAC_L1(R89) .

If I do mute R43 in the previous register, I can hear the white noise.

In our app, DAC_L1 is used for a melody ring play from CPU.

This DAC_L1 is mixing for Right LOP/M with PGA_L(R88). 

The PGA_L(R88) is connected to R15 PGA / MICx by bypassing ADC and 3D processing block. This is used for voice path.

So the melody ring or voice can be played on Right LO .

Under this condition, If we disconnect or mute DAC_L1(R89), white noise is disappear. 

Seemingly, the issue seems to be DAC_L1(R89) itself. (Currently 0dB setting)

The white noise is not a specific narrow band sound. It's pure white noise.

In a case, when I tried to do below, the noise is disappeared.

1. powered down - DAC_L1(R37.7) 

2. Set  volumes, gains in that audio path.

3. Route DAC_L1(R89.7)

4. Set Volume - DAC_L1(R89.6:0)

5.powered up DAC_L1(R37.7).

--> I can't hear the white noise in this case. However, this way is always not effective in every voice path case.

And the noise level is depending on R109 (0--> 50% -->100% is more loud).

Currently we are using DAC_L1(R89, 0dB) , Right LO(R93, +1dB). for the melody ring path

Decreasing R89 and increasing R93 are another option to improve the white noise. But I'd like to improve DAC_L1 noise first.

Please advise me about this issue

This is our audio block.

Best regards

Byunghee Sohn

Dear TI Support Team.

I have tested this one for another path below.

I tested DAC_R1 instead of DAC_L1. But it's the same result

And after disconnecting DAC_L1, DAC_R1, I routed DAC_R3 with PGA_L.

However, white noise became louder than DAC_L1/ DAC_R1.

Can you advise me about this?

Best regards

Byunghee Sohn

Hi,

I'd expect the same from either DAC. Here are a couple of suggestion you can do:

• Change your word length or bit depth from 16 to higher even to 32
• Minimize your digital volume side and use your analog gain to compensate

Regards.

Hi 

Thank you so much for your reply.

I'd like to know if the word length(16bit) can have an noise issue on DAC.

Is there an issue on 16 bit word length ?

In case of our application, data coming from Host I2S is fixed to 16bit.

I also think that adjusting the digital gain and analog gain become an solution.

However, I want to find out what the issue of the noise is.

Regards

B.H. Sohn

Hi,

It's not that 16 bit causes noise issue on DAC, but rather the quantization noise is better with larger bit depth.

You can search the web on this topic.

As proposed above, you can use whichever method that works better for you.

Regards.

Hi 

Thanks for the exploration.

We now used Low-pass filer in 2.4 Out-of-Band Noise of "SLAA749" that you recommended.

And we can see the noise is almost removed under loud noise condition (high vol, 100% @ R109)

You can close this ticket.

Many thanks

Byunghee Sohn