Question
What are the filter requirements for my application?
Answer
There are as many valid solutions as use cases. Please review section
´Applications Information´ and ´Application Circuits´ at the end of the AD8232
datasheet for a quick introduction to several different use cases and contact
the AD8232 support for additional questions or help.
Having said that, there are two configurations worth starting from:
In applications where only the heart rate is measured (peak detection) and
the actual ecg waveform is not important you can afford to narrow the passing
band. We recommend a 7 to 25HZ filter. Since the frequencies below 7Hz are
attenuated, this solution is very reliable against movement and therefore
recommended for sports applications.
In applications where the shape of the ecg waveform is important a 0.5Hz to
40Hz bandwidth is recommended. This is known in many places as ECG Monitor
Bandwidth. Since such low frequencies go through the pass band, this solution
is quite sensitive to motion artifacts and base line wandering.
Second order filters are proposed by default because they offer a good tradeoff
between component count and distortion. For lower component count and softer
attenuation in the rejected bands a single order filter will do. For steeper
transitions a third order filter can be implemented just adding an additional
RC couple.
