ADS114S06B: Filtering Digital Power to Analog

Hi Russell,

you are correct, you often see customers placing ferrite beads in the power supply lines to separate analog and digital supplies. I am personally not aware of any specific literature which discusses this topic, but I am almost certain someone has written something about it already.

For our precision ADCs however we usually don't recommend any sort of inductance on the power supply lines. Main reason is that the digital circuitry of our ADCs can draw short spikes of current. With inductance in line on the power supply those spikes can cause the supply voltage to droop, potentially even below the reset threshold of the ADC. This can then cause unwanted resets or issues during power-up of the ADC.

Using a single 3.3V supply that is created by an LDO for all three supplies (AVDD, IOVDD, DVDD) of the ADS114S06B is perfectly fine.
If you want you can place a small resistor between the analog supply and the digital supplies, but it is most likely not required. More important is proper power supply decoupling. Means place a >=330nF cap as close to the AVDD pin and a 100nF cap as close to the shorted IOVDD and DVDD pins as possible. You may want to add another larger bulk capacitor in parallel if you want. But your LDO probably has a larger output cap anyway already.

Regards,