TLV320AIC3204: PGA input referred noise

Marijn Hasebos

Part Number: TLV320AIC3204
Other Parts Discussed in Thread: TLV320ADC3101

Tool/software:

Hi,

I have a question about the input noise of the PGA.

The datasheet mentions the following (page 11) about the input ferered noise of the PGA, when the AD converter is bypassed:

At 40dB gain the input referred noise (A-weighted) is 3.4uVrms, under the following test conditions:

- Channel Gain = 40dB

- input Signal (0dB) = 5mVrms

- Inputs ac-shorted to ground, Input Referred

What I do not understand, is the test condition "input signal 5mVrms". How can this signal be fed into the PGA, when the inputs are ac-shorted to ground?

The second question is about the "idle channel" noise, which is speified to be 7uVrms (A-weighted). The test conditions are as follows:

- idle Channel

- IN1_L and IN1_R ac-shorted to ground

What gain is configured at the PGA for 7uVrms noise? The datasheet does not mention this.

For simulation purposes I am interested in the input referred noise of the PGA. Can I use the either of these values for a worst case input referred noise of the PGA?

Regards,

Marijn

1 month ago

0 Jeff McPherson 1 month ago

TI__Mastermind 30685 points

Hi Marijn,

The Input Referred Noise is measured by shorting the inputs to ground and then injecting a noise source onto the inputs (the 5mVrms signal). This controls the noise source so that the Input Referred Noise can be measured accurately.

In the Device Setup row, just above the one you shared, it is stated that the Channel Gain is set to 0dB. So the Idle Channel noise test is taken with 0dB channel gain.

If you are interested in input referred noise, then use the input referred noise spec (3.4uVrms). The idle noise test is not input referred.

Best regards,
Jeff McPherson

0 Marijn Hasebos 24 days ago in reply to Jeff McPherson

Prodigy 20 points

Hi Jeff, thank you for your response.

The input referred noise specification (3.4uVrms) is at 40dB PGA gain. Are more measurements available? For example at 0dB, 10dB, 20dB and 30dB gain?

The TLV320ADC3101 datasheet does feature this information (Input-Referred Noise vs PGA Gain, figure 9). (link: Datasheet TLV320ADC3101).

Thank you in advance.

Marijn

0 Jeff McPherson 24 days ago in reply to Marijn Hasebos

TI__Mastermind 30685 points

Hi Marjin,

Unfortunately the specific test points of 0, 10, 20, etc are not available. However you can extrapolate from the plot the referred noise.

Best regards,

Jeff McPherson

0 Marijn Hasebos 8 days ago in reply to Jeff McPherson

Prodigy 20 points

Hi Jeff, sorry for getting back to you so late.

If I understand correctly (and please correct me if I'm wrong) the input referred noise is calculated as follows: input_ref_noise = Output_noise/gain.

So when using the 3.4uVrms input referred noise @ 40dB gain (100x), the output noise would be:

Output_noise = input_ref_noise*gain → 3.4uVrms*100 = 340uVrms or -69.37dB (A-weight).

Am I correct?

Regards,

Marijn

+1 Jeff McPherson 8 days ago in reply to Marijn Hasebos

TI__Mastermind 30685 points

Hi Marijn,

Yes that's correct.

Best regards,
Jeff McPherson

0 Marijn Hasebos 7 days ago in reply to Jeff McPherson

Prodigy 20 points

Hi Jeff,

Thank you for your help.

Regards,

Marijn

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TLV320AIC3204: PGA input referred noise