INA217: Hum noise in Audio pre amplifier ( INA217AIDWT )

Hi Lakshmanan,

haven't we discussed the same issue a while ago? Can you give a link to that thread?

Kai

Hello Kai,

Yes we discussed same issue in the following link
e2e.ti.com/.../698716

Ok, I will follow old thread.
We will discuss the hum noise issue using old thread.

Regards
Lakshmanan V

Hi Lakshmanan,

I can only repeat myself:

e2e.ti.com/.../2580116

Kai

Hi Lakshmanan,
In addition to Kai's suggestion of removing the charge pump from the circuit to troubleshoot, can you rule out a PCB layout issue as the source of this noise? The fact that the noise disappears when the XLR inputs are shorted suggests that it's possible noise is capacitively coupling into the inputs of the INA, possibly from a nearby noisy power supply trace or data line.

Hello Alex Davis & Kai,

  

             At present we are giving +5 Volts supply to INA217 taken from USB power adapter.

 And -5V generated from Charge pump regulator & given to INA217

Instead of giving ±5V to INA217, We have plan to give ±4.5V to INA217 using LDO regulator.

We have plan to use 4 layer PCB. So we provide solid ground plane.

So please give me the suggestion to proceed further.

Thanks & Regards

Lakshmanan V

Hi Lakshmanan,

have you made the testing I recommended? What is the result?

Kai

Hello sir,

     As of now we don't have the board for testing.

we don't have pad in the board to create the LPF for filtering power supply noise.

So, we are planning to go next revision of this board.

Please suggest us for changes in the next revision.

Thanks & Regards

Lakshmanan V

Hi Lakshamanan,

Any additional recommendations I could make at this point would require access to the PCB for testing, as there are a few possible sources (as we've discussed earlier in this thread). If you're unable to troubleshoot further, I don't think there's any recommendation I can make that I haven't already. I'd suggest all the following:

1. Improve filtering in the power supply connections to the INA217. If possible, power the INA217 from a linear regulator to further reduce power supply noise.

2. Ensure that "ground islands" don't exist in your layout. If, for example, the ground connections C42, C43, R7, and D3 all connected to each other but didn't connect back to the global USB_GND_CODEC, noise present on the P5V_USB supply would couple into the inputs of the INA217, and this coupled noise would go away when the INA inputs were shorted. If you're doing the layout on a 4-layer stackup with a dedicated ground, this shouldn't be an issue.

3. Ensure that noisy, high speed signals (USB data connections, USB +5V, switching power supply rails, etc) are routed far away from the sensitive analog inputs to the INA217.