TAS5825M: VR_DIG ofen was output abnormal voltage 0.64V when power on, and then due to not work properly。

Hello Customer,

Your pictures can not be see, can you upload with zip file?

If VR_DIG is only 0.64V, I2C module does not work. 

Can you share information below for our further debug:

1. What is your DVDD voltage?
2. Can you share your schematic of TAS5825？
3. For power on sequence, can you check whether sequence below is followed?

BR

Alix Wan

Dear Alix

What is your DVDD voltage?

1.8V

Can you share your schematic of TAS5825？

OK,please to see the attachment

For power on sequence, can you check whether sequence below is followed?

https://e2e.ti.com:443/the picture was not display,please to supply a attachment.I will to check it.TAS5825 issue 07_27_2020.doc

Hi Customer,

Please do an experiment: changing your power-on sequence as below:

1. please do not provide I2S before PDN is pulled high;
2. Make sure >=5ms delay after PDN is high;
3. Then enable I2S and do I2C initialization when I2S clcoks are stable 

Let me know if this issue still be there.

BR

Alix Wan.

Dear Alix

Please to see the attachment

Our power-on sequence was meet your suggestion, but due to the VR_DIG output abnormal 0.64V, so the I2C communication was not receieve the ACK from the TAS5825.

I should  add more information:

1.  I found one pcs abnormal chip as mention, VR_DIG output abnormal 0.64V;

2. This unit returns from Customer,We want to know why only this chip output 0.64V from VR_DIG at power on.

The datasheet only  mentions the /PDN (power down pin of the PA device) is required to keep high for 5ms at least before I2C communication starts. but it doesn’t mention how long to keep /PDN low before enabling the PA chip. When we kept low by driving the /PDN from 50ms to more than 1s through GPIO, VR_DIG could output 1.5V normally and the chip just worked fine.

Thanks 

TAS5825 issue 07_27_2020 (2).docDear Alix

Please to see the attachment

Hello Alix

You means pullup AVDD to DVDD with 61.9K resister？IF VR_DIG will output normal voltage, and then AVDD will output 5V, it is whether or not due to the chip was broken? And this hareware solutionit it is difficult to finish it, I should to break off the 1V8 power net , and string in the diode to prevent the 5V poured to 1V8 power net.

Because i have only one sample. If this is indispensable and not lead the IC broken, i will try my best to achive this solution.

And I want to know the purpose of the hardware solution.  

Thanks

Yun

Hi Yun,

Based on your comments before, this issue seems to be occur in your board easily, right?

I am wondering:

1. If you change the 1.8V DVDD to 3.3 V DVDD, will this issue still be there. But considering your board design, it may not be able to do this experiments.
2. My hardware solution above is :
   1. I deduce that some leakage current prevent VR_DIG brings up from 0V to 1.5V.
   2. hence, pullup VR_DIG to AVDD.to help VR_DIG can help on this 
   3. The solution above will not damage the device per my confirmation

BR

Alix Wan.

Hi Alix

Yes, this issue seems to be occur in your board easily.

But I have one question, VR_DIG was output after AVDD output, The interval was 27s in my board and SW, the kernel system was startup and then to setting the TAS5825M, and then AVDD was output.

Do yout theink this is workable?

I will check the VR_DIG pull to AVDD with 61.9K

Yun

Hi Yun,

Any update for hardware solution?

BR

Alix Wan.

Hi Alix

The VR_DIG output was normal when power on after HW change today, but i should to do more test. 

And then ,i will supply the final test result.

If you have any suggestion please to tell me,i will to check it.

Thanks

Yun