How to deal with noise on mixed Signal IC design

[Robert Qi]

Dear All,
How to prevent digital swithcing noise from disturbing analog circuits?
Should I use Deep N-well to envelop all digital circuits as someone's advice?
Or envelop all analog circuits?

any other methods to deal with the noise between digital and analog?

Thanks in advance

Robert

 

[A.Anand Srinivasan]

isolation between the power supply and ground of the analog and digital part can avoid a lot of noise coupling,....

 

[abcyin]

first, envelop blocks seperately by guard ring, then deep trench is a way to isolate the analog and digtal parts of the chip.

 

[eka_a_k]

You can use Ferrite Beads to isolate analog Vcc from digital Vcc. Read it here http://www.sigcon.com/Pubs/edn/ferritebeads.htm.

 

[A.Anand Srinivasan]

You can use Ferrite Beads to isolate analog Vcc from digital Vcc. Read it here http://www.sigcon.com/Pubs/edn/ferritebeads.htm.

i think using ferrite beads is an apt solution for PCBs.... but i think Robert is talking about ICs when is mentioning about trench and well.....

 

[she_long]

I have the same question.
I think analog blocks is the most sensitive circuit, they must be isolate from the digital circuit. The first is use the different VDD and GND for analog/digital. And second Nwell or space is two ways to isolate the different blocks, but there's a trade-off between die size and isolation, and adjacent the Nwell, there must be a P+ Pickup envelop Analog block to absorb the substrate noise.

 

[northeast1]

Dear All,
How to prevent digital swithcing noise from disturbing analog circuits?
Should I use Deep N-well to envelop all digital circuits as someone's advice?
Or envelop all analog circuits?

any other methods to deal with the noise between digital and analog?

Thanks in advance

Robert

deep N well, guard ring, enlarge the distance between digital and analog.

 

[selvaraja]

dual guard ring for analog block for better isolation.

 

[PaloAlto]

isolation between the power supply and ground of the analog and digital part can avoid a lot of noise coupling,....

I can't agree more. If your application is over a couple of dozens of MHz, unless you do a really careful design of the power supply lines, you will see lots of switching noise from the digital part.

Pay especial attention to the digital pads, they really are noisy

 

[Sadegh.j]

hey

check the attached file.

 

[lijianheng]

Separate power of different module and add guard ring.

 

[PaloAlto]

Sadegh.j

Could you put the rest of the doc? Or maybe give a reference to see where it comes from, I would like to read more about that backplane

thanks

 

[heng155]

guard ring for sensitive analog part, seperate vcca & vccd, decoupling capacitences for vcca (especially sorround sensitive analog circiut), decoupling capacitences for very big inverters ,add decoupling caps on your unused space , shied your long wire dc bias with power supply wire