ADC12DJ5200RF: Input anti-aliasing filter concern

Peter Cheng

Part Number: ADC12DJ5200RF

Off-the-shelf low pass filter (LPF) are all single-ended components. Will these components introduce excessive time offset between IN+ and IN- signals? In my design, the circuitry in the analog path are all differential, so there is no opportunity to LPF the signal while it is still single-ended.

Is there such a thing as differential LPF component that is off-the-shelf in the market?

over 2 years ago

0 Neeraj Gill over 2 years ago

TI__Mastermind 20541 points

Hi Peter,

You might be able to use the these low pass filter. They are single ended so you will need one + and -ve signal.

https://www.johansontechnology.com/low-pass-filters

Regards,

Neeraj

0 Peter Cheng over 2 years ago in reply to Neeraj Gill

Prodigy 70 points

Neeraj, so it sounds like there is no mismatch concern using single-ended off-the-shelf LPFs?

0 Peter Cheng over 2 years ago in reply to Neeraj Gill

Prodigy 70 points

Neeraj, so it sounds like there is no mismatch concern using single-ended off-the-shelf LPFs?

0 Rob Reeder over 2 years ago in reply to Peter Cheng

TI__Mastermind 20060 points

Hi Peter,

Yes, there will be mis-match between the two inputs if you use a single-ended filter on each input independently. This will give rise to even order distortion over input frequency because of the phase mis-match between the two inputs..

Is there a reason you cannot design a differential filter instead? Or are you constrained by pcb space and cannot use too many components?

I am not sure, there are any differential filters on the market these days. Several companies did start offering solutions, but there weren't many customers using them. So I believe they stopped those developments.

Regards,

Rob

0 Peter Cheng over 2 years ago in reply to Rob Reeder

Prodigy 70 points

Thank you Rob. I just wanted to confirm that using a differential filter is the much preferred solution. I was hoping to find them online but to no avail. So my only option now is to custom design a high order LPF.

0 Rob Reeder over 2 years ago in reply to Peter Cheng

TI__Mastermind 20060 points

Hi Peter,

Unless there is specific design criteria that you need to meet, typically a 3rd order filter will do the job.

Higher order filters can create issues with too many component mis-matches. Please keep that in mind.

Regards,

Rob

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ADC12DJ5200RF: Input anti-aliasing filter concern