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I'm designing a low-noise audio gadget that uses an MCP3008 ADC (for sensors) together with a Raspberry Pi and a PCM5102a high quality DAC. The PCM5102a is powered by a 3.3V LDO. I'm wondering if I should share that same LDO to also power the MCP3008 or should I just use the pi's onboard 3.3V?
The MCP3008 is already using a precision 1V reference voltage IC. Is it necessary to use a low noise 3.3v power supply as well or will it make no difference?
If I use the LDO to power both chips, will the MCP3008 generate noise that will disrupt my (very very low noise) PCM5012a?
The PSRR on the MCP3008 is about -68db whereas on the PCM5102a it's around -100db!
The alternatives are to a) just power the MCP3008 from the Pi's onboard 3.3V supply, or b) use a separate 3.3V LDO, but that seems like overkill.