Hi Marco, The source for the supplies on the ADC is not limited, but a clean power supply is always recommended especially for AVDD, otherwise, it will degrade the performance specified in ADC's datasheet because the power-supply rejection ability(PSRR) on the ADC is variable and limited with ripple/noise frequency, please refer to the below graph from ADS8689 's datasheet, this is the reason why we often use LDO to provide a clean analog power supply to ADC on our EVM boards or reference designs, for example, TPS7A4700 or TPS7A4901. I hope this explanation is helpful for you, thanks. Best regards Dale
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