PGA2311: PGA2311 power supply

Briquel Florian

Part Number: PGA2311
Other Parts Discussed in Thread: TPS7A49

Hello,

I'm designing a high end quality A class amp and would like to use PGA2311 to add digital volume control.

My design has separate analog ground for both channel in order to keep a very high channel seperation. Then I have few questions about the power sheme possibility of PGA2311.

First question: is it possible to have separate ground for PIN 10 and PIN 15? In fact I use small value resistor (0.1R) to isolate left and right channel ground this leading to a voltage drop around 0.15V for each channel when amp is ON (my general ground is connected to both 0.1R resistors to create channel left groung and channel right ground), this leading to a 0.3V voltage drop between PIN10 and PIN15, it's OK for PGA2311?

If i'ts OK to have separate voltage level between PIN10 and PIN15 how I connect bypass capacitors C3,C4,C5,C6 ?

Note: I use low noise LDOs (TPS7A49/30) to generate +/-5V analog rails for PGA2311, the ground reference level for these rails is my general ground.

Thanks for help!

Best regards,

Florian

over 6 years ago

0 Alexander Davis over 6 years ago

TI__Expert 6250 points

Hi Florian,
I think it should be okay to have a small voltage difference between the two AGND pins, though since there is no specification in the datasheet, it's possible there's an impact on performance I haven't considered. If I understand your application correctly, you'd have a 0.1Ω resistor from each channel back to the global power ground, so if both channels consumed the same current, both ground connections would be around the same voltage.

I'd recommend tying the bypass capacitors on your power supplies back to your global power ground.

0 Briquel Florian over 6 years ago in reply to Alexander Davis

Intellectual 280 points

Hi Alex,

Thanks for very fast answer! Yes you understand my app.

Indeed the datasheet did no mention about separate ground, I think if there is two separate pins and two separate names (aigndl and aigndr) it's for this kind of purpose?

Maybe an ex burr brown designer can validate/unvalidate this?

For the bypass capacitor OK it make sense to connect them to the global power ground.

Best regards,

Florian

0 Alexander Davis over 6 years ago in reply to Briquel Florian

TI__Expert 6250 points

Hi Florian,
Unfortunately, the designers who worked on the PGA2311 are no longer available. Asking around, there doesn't appear to be any obvious cause for concern with having a small difference between the two AGND pins, so long as both ground pins remain within the PGA's supply range. That said, since there's no datasheet specification to back it up, it's not something we can guarantee.

0 Briquel Florian over 6 years ago in reply to Alexander Davis

Intellectual 280 points

Hi Alexander,

Ok will give it a try then.

Thanks

Regards

Florian

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PGA2311: PGA2311 power supply