PCM1795 / THD+N at DSD mode

S.Satoshi

Other Parts Discussed in Thread: PCM1795, PCM4222

Hi,

Our customer are evaluating PCM1795 right now and they are measuring THD+N at DSD mode with 128 fs. The datasheet specifies it at only 64 fs, so they understand that it's not guaranteed at 128 fs. But they hope to have the THD+N data at DSD mode with 128 fs just for their reference. Because they measured at the condition but they have not gotten expected result as below.

1, THD+N = 0.03% at 0dB with 20k LPF

2, THD+N = 0.002% at -3dB with 20k LPF (Getting better compared with #1)

As stated above, they have not had good result at 0dB, so it will be appreciated if we can have your advice about it.

Best Regards,

Sonoki / Japan Disty

over 12 years ago

0 Don Dapkus over 12 years ago

TI__Guru**** 189401 points

Hi, Sonoki,

We will get you this data ASAP, hopefully before the end of this week.

-d2

0 S.Satoshi over 12 years ago in reply to Don Dapkus

Guru 21685 points

Hi, Don-san,

I appreciate for your support.

Could you let me know the test condition you are planning to take data? I will show our customer the test condition and confirm if it will be acceptable for them in advance.

Best Regards,

Sonoki

0 S.Satoshi over 12 years ago in reply to S.Satoshi

Guru 21685 points

Hi, Don-san,

I'm sorry for rushing you, but I would like have your update about this request.

And also could you please give us your comment for additional question for DSD filter. They are asking if DSD filter 1-4 will give the difference of THD+N performance at 0dB full scale so appreciate your comment on this point also.

Your quick response will be appreciated.

Best Regards,

Sonoki

0 S.Satoshi over 12 years ago in reply to S.Satoshi

Guru 21685 points

Hi, Don-san,

Now I'm requesting some request in each post, and then I would like you to give your first priority for this post.

Your understanding will be appreciated.

Best Regards,

Sonoki

0 Patrick Galvin over 12 years ago in reply to S.Satoshi

TI__Genius 16270 points

Satoshi-san,

I have attached a screenshot of THD vs Freq when the DSD data is 64xFs and 128xFs and 0dB amplitude. There is about a 3dB difference between the two, but no drastic performance degradation to 0.03% (or roughly -70dB). I use Filter - 2 when in DSD mode. Since changing the FIR filter will change current output, there is some difference in THD performance, but when I test through all four filters I cannot produce THD+N that is close to 0.03%, and there is not much change from the attached graph.

0 S.Satoshi over 12 years ago in reply to Patrick Galvin

Guru 21685 points

Hi Patrik-san,

I appreciate for your support.

I sent your data and then I received one question about setting of PCM1795. Which value did you set on OS[1:0]: Analog-FIR Operation-Speed Selection? I believe that you set it as default value but please let me know if you did not set default.

Best Regards,

Sonoki

0 Patrick Galvin over 12 years ago in reply to S.Satoshi

TI__Genius 16270 points

Satoshi-san,

I set it as default, and then used the PCM4222 "DSDMODE" pin to send 64xFs DSD data or 128xFs DSD Data.

0 Don Dapkus over 12 years ago in reply to Patrick Galvin

TI__Guru**** 189401 points

Hi, Sonoki,

Did we answer all your questions here? Can we close this thread?

-d2

0 S.Satoshi over 12 years ago in reply to Don Dapkus

Guru 21685 points

Hi Don-san,

I'm sorry for delayed response for this thread. I have had your answer for this thread so please close this thread. Now I'm waiting for your response for thread named RE: PCM1795 / AMPLITUDE vs FREQUENCY at PCM mode.

Best Regards,

Sonoki

0 hiroyuki over 12 years ago

Prodigy 130 points

Hi Don-san

Our customers are also considering the use of the same (DSD mode with 128 fs.)
for the PCM1795. They would like to measure the performance of the PCM1795 by themselves.
Please tell me how to measure this data.
Please tell us how to connect PCM1795 to PCM4222 EVM.

Best Regards,

H.Ogawa / Japan Disty