ADC3908S065: Filter Design

João Rego

Part Number: ADC3908S065

Tool/software:

Hello,

I have a design with the ADC39085S065, where I didn't use any filter at AVDD and IOVDD (I just placed some decoupling capacitors). Since I am getting more ripple than expected at the digital signal, I think I should add a filter to each supply. Do you think this higher ripple might come from not using a filter on the supplies? If so, could you propose a ferrite bead and an EMI filter for the ADC supplies?

Also, do I have to use the 100 Ohm series resistor on the digital signals?

Thank you.

1 month ago

0 Rob Reeder 1 month ago

TI__Mastermind 41200 points

Hi Joao,

Yes, please use 100ohm series resistors on each of the outputs. This helps directly with EMI and digital switching in the system.

You can read this article about why this should be done.

https://www.analog.com/media/en/training-seminars/design-handbooks/Practical-Design-Techniques-Sensor-Signal/Section10.pdf

see page 14

On the power supply, filtering will help on each of the analog and digital supplies. You can use the ADC's EVM schematic and BOM for material recommendations and how the power supply was implemented.

If you want to send us a schematic of your power supply as it is now, we can make some comments there too.

Please advise.

Regards,

Rob

ADC3910D125_RevE2(001)_BOM.xls

4251.ADC3910D125_RevE2(001)_Sch_2024-04-08.PDF