Powering Analog circuit through SMPS.

SMPS output has ripple and switching noise at its output. Such a supply could hamper performance of high resolution slow speed analog circuit.How to reduce it? A low noise linear regulator would do? An LC filter can work or both( LC filter followed by linear regulator)? A ferrite bead is also a general practice."Please suggest me how should i power my slow speed high resolution analog hardware(i am talking about process control, mainly temperature measurement applications)".

This is a very interesting topic and one that's hard to answer in a few lines of text.

First you should look at the datasheets of the part you are using to identify if there is a recommended power solutions, then identify the PSRR curves in the datasheet if they are available.

As a general rule if you signal of interest is in <100Khz most part have very good PSRR and the power domain does not need to be extremely clean. For parts with much higher bandwidth and signals in the 1Mhz to 1Ghz then noise from the power supply needs to be managed in multiple ways, filtering and LDOs.

If you are dealing with parts that are sensitive to noise at any frequency such as PLLs and VCOs then everything needs to be designed with low noise in mind.

We have some design examples in what we called the circuits from the lab section of our web site

http://www.analog.com/en/circuits-from-the-lab/CN0147/vc.html

http://www.analog.com/en/circuits-from-the-lab/cn0201/vc.html

http://www.analog.com/en/circuits-from-the-lab/CN0234/vc.html

http://www.analog.com/en/circuits-from-the-lab/CN0183/vc.html

Finally I recently recorded a session for ADI's Virtual Conference DC-13 that addressees exactly this topic.

This FAQ was generated from the following discussion: Powering Analog circuit through SMPS.