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Filtering with Delta Sigma ADCs (It’s built in!) | Cypress Semiconductor

Filtering with Delta Sigma ADCs (It’s built in!)

I just had a customer ask me to help them design 1.5kHz low pass filter to place in front of their 5ksps ADC. What they neglected is that a DelSig ADC has a built in low pass filter. It is its decimator. If it is an incremental (1st order sinc filter) then in looks like a low pass filter with a 3db point at 44% the output rate (2.2kHz for 5ksps) and 36% for a 2nd order decimator (1.8Hz for 5ksps).  If you wanted a filter at 1.5kHz then set the output rates to 3.4ksps (1.5kHz/.44) or 4.2ksps (1.5kHz/.36) respectively.
 
There may be disadvantages to using a averaging ADC but when you can exploit the benefits, you should do so!

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