TAA3020: SNR at SE input with PGA gain

Hello,

Here is additional data point of +12dB gain setting which is specified differential mode SNR on the datasheet.

What is SE mode SNR at +12dB condition of your design target specification?

There is 7dB additional noise come from analog gain block compared with differential mode.

Regards,

Mochizuki

Hi Mochizuki-san,

Let me get back to you on this by early next week.

Thanks and Regards

Lakshmi Narasimhan

Hi Mochizuki-san,

Along with Differential/Single-ended, can you also mention the input impedance and coupling (ac/dc) settings?

If possible, can you share the device configuration scripts during these tests?

Thanks and Regards,

Lakshmi Narasimhan

Hi Lakshimi,

We are using TAA3020EVM with AC coupling input to AP signal output which is 50 ohms SE an 100 ohms at Diff.

Register setting is default value of PPC3, just switch input mode SE or Diff.

We can see PGA noise performance as below on TLV320ADC3140.  Is that similar performance on TAA3020 too?

Regards,

Mochizuki 

Hi Mochizuki-san,

Let me look into the SNR for AC-coupled inputs and get back to you by end of the week.

Can you also confirm that the differential and single-ended connections were made as per datasheet diagrams?

Thanks and Regards,

Laksmi Narasimhan

Laksmi-san,

Yes, the conecction is correct, we are using EVM as it is.

Any update from your side?

Regards,

Mochizuki

Hi Mochizuki-san,

Here is the expected deltas in A-weighted SNR for AC-coupled inputs:

1) With 0dB PGA Gain, the difference between Differential and Single-Ended SNR is ~3.4dB.

2) With 12dB PGA Gain, the difference between Differential and Single-Ended SNR is ~6.5dB.

3) With differential inputs, the difference between 0dB and 12dB SNR is ~7dB.

Thanks and Regards,

Lakshmi Narasimhan

Lakshimi-san,

Our mesuerment result has discrapncy from your expectation. What is your verification data?

1) With 0dB PGA Gain, the difference between Differential and Single-Ended SNR is ~3.4dB.　-->8.6dB

2) With 12dB PGA Gain, the difference between Differential and Single-Ended SNR is ~6.5dB. -->15.5dB 

3) With differential inputs, the difference between 0dB and 12dB SNR is ~7dB.  --> 3.5dB

Regards,

Mochizuki

Hi Mochizuki-san,

This was checked on an EVM, with different configurations and PGA Gain settings.

These are a-weighted measurements.

Can you share the configuration scripts used for testing SNR of each condition?

Thanks and Regards,

Lakshmi Narasimhan

Lakshmi-san,

Thank you very much for the information.

Attached file is capture of PPC3 setting.TAA3020 cnfg.xlsx

Regards,

Mochizuki 

Hi Mochizuki-san,

Let me confirm on this setting and follow up.

Also, an additional clarification, are we measuring SNR with input AC-signal shorted to GND as per the condition mentioned in the datasheet?

Thanks and Regards,

Lakshmi Narasimhan

Lakshim-san,

Is that meaning that IN1 pin signal source impedance is critical factor for TAA3020 PGA SNR even 0-ohm AC short and 50-ohms AP signal output makes +6dB larger noise?  

If so, what is real world application SNR with 600-ohms microphone input at +12dB PGA gain?

Regards,

Mochizuki