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PCM1865-Q1: Accuracy of the PGA + ADC of PCm186x

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yoshiki hasebe

Replies: 8

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Part Number: PCM1865-Q1

Dear Sirs,

My customer asked us about Accuracy of the PGA + ADC and Matching between PGA + ADCs onchip of PCm186x.

What are these specifications?

Each of these values is described only as a typical value.
Is there a maximum value?

Does this accuracy affect the change of FS?

Best Regards,

Y.Hasebe

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Diego Melendez
- Dec 7, 2017 12:13 AM
Hi, Hasebe-san,

We only specify the typical value for these specs, the maximum value for them is not typically specified. Sampling rate should not affect the accuracy of the PGA or viceversa.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer
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yoshiki hasebe
- Dec 7, 2017 6:14 AM
In reply to Diego Melendez:

Hello Diego-san,

Thank you for your reply.
I understand your comments.

By the way there was an additional question from my customer.

In the pcm 186 x series, the group of PCM 1860 - Q 1, PCM 1862 - Q 1, PCM 1864 - Q 1 and the group of PCM 1861 - Q 1, PCM 1863 - Q 1, and PCM 1865 - Q 1, the SNR min value is 97 dB
It is the same value.
Is this correct?
Please let me know the reason if this is correct.

Best Regards,
Y.Hasebe
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yoshiki hasebe
- Dec 7, 2017 6:39 AM
In reply to yoshiki hasebe:

Hello Diego-san,

I'm sorry for asking so many questions.
My customer asked additional questions.

1.Can I consider the value of Accuracy of the PGA + ADC and Matching between PGA + ADCs onchip a range of variation?

2.Do conversion variations occur due to variations in the supply voltage to the IC?
　Please let me know the range of variation if it occurs.

3.If the gain is changed with the PGA circuit, will it affect the input impedance?

4.Is there SNR data when changing the PGA gain?
　They want to know the SNR at PGA Gain = 9 dB.

Best Regards,
Y.Hasebe
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Diego Melendez
- Dec 7, 2017 7:37 PM
In reply to yoshiki hasebe:

Hi, Hasebe-san,

Please refer to my comments below:

0- Correct, the minimum SNR spec of all the PCM186x family of ADCs is 97dB.

1- The accuracy and matching spec indicates the largest variation that could be expected between devices.

2- Voltage variations should not affect the conversion as long as the recommended operating conditions are met.

3- The input impedance should not change with the PGA gain variation.

4- The PGA gain change affects some specs like THD and SNR, this is already specified in the datasheet. Unfortunately e don't have specific data for 9dB gain, but it should be above 100dB.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer
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yoshiki hasebe
- Dec 8, 2017 1:03 AM
In reply to Diego Melendez:

Hello Diego-san,

Than you for your kindly reply.

0- Correct, the minimum SNR spec of all the PCM186x family of ADCs is 97dB.

⇒I think simply, it seems that the group of PCM1683-Q1 is wider than the group of PCM1680-Q1.

　(Because it is the description of only Min & Typ, so that condition)

　Can I think that the group of PCM1683-Q1 is wider than the group of PCM1680-Q1 in Spec range?

　If so, they are worried that the variation range of the PCM 186x_A group will be as wide as 97 dB - 110 dB.

　Also,in the single-end condition, the MIn. Value is not described.

　Please let me know the reason.

1- The accuracy and matching spec indicates the largest variation that could be expected between devices.

⇒I understand it.

2- Voltage variations should not affect the conversion as long as the recommended operating conditions are met.

⇒I understand it.

3- The input impedance should not change with the PGA gain variation.

⇒I understand it.

4- 1The PGA gain change affects some specs like THD and SNR, this is already specified in the datasheet.

⇒Please tell me something about the influence of THD and SNR by changing PGA gain.

　I can only find values of 0 dB and 32 dB condition on the Sepc table on page 12.

4-2 Unfortunately e don't have specific data for 9dB gain, but it should be above 100dB.

⇒I understand it.

Best Regards,

Y.Hasebe
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yoshiki hasebe
- Dec 13, 2017 1:12 AM
In reply to yoshiki hasebe:

Hello Diego-san,

There are still two questions with the above reply contents.
Please let me know about the questions of No. 0 and No. 4 - 1.

No.0:

0- Correct, the minimum SNR spec of all the PCM186x family of ADCs is 97dB.

⇒I think simply, it seems that the group of PCM1683-Q1 is wider than the group of PCM1680-Q1.

　(Because it is the description of only Min & Typ, so that condition)

　Can I think that the group of PCM1683-Q1 is wider than the group of PCM1680-Q1 in Spec range?

　If so, they are worried that the variation range of the PCM 186x_A group will be as wide as 97 dB - 110 dB.

　Also,in the single-end condition, the MIn. Value is not described.

　Please let me know the reason.

No.4-1:

4- 1The PGA gain change affects some specs like THD and SNR, this is already specified in the datasheet.

⇒Please tell me something about the influence of THD and SNR by changing PGA gain.

　I can only find values of 0 dB and 32 dB condition on the Sepc table on page 12.

Best Regards,

Y.Hasebe
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Diego Melendez
- Dec 15, 2017 10:01 PM
In reply to yoshiki hasebe:

Hi, Hasebe-san,

Sorry for the delay. As you mention, the PCM1863-Q1 has a wider range as the SNR is higher for these parts. The SNR spec of the device in single-ended mode was not part of the device characterization, but it should be around 95dB for all the parts of the PCM186x family.

Only the maximum and minimum SNR are provided on the datasheet, in general the noise level will increase with the PGA gain increase, to mitigate this effect, the PCM186x devices have an internal lookup table to configure the analog and digital PGAs with the optimal performance combination.

Best Regards,

-Diego Meléndez López
Audio Applications Engineer
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yoshiki hasebe
- Dec 18, 2017 2:45 AM
In reply to Diego Melendez:

Hello Diego-san,

Thank you for your reply.

I understand your comments.

I will explain them to my customer.

Best Regards,

Y.Hasebe
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