Filtering with Delta Sigma ADCs (It’s built in!) | Cypress Semiconductor
Filtering with Delta Sigma ADCs (It’s built in!)
July 27, 2011
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!