Q
What is the benefit of the Fast Restore feature?
A
The AD8232 implements an AC-coupled solution. This means it removes the dc and
near-dc frequencies via a high pass filter. The time required to remove dc
offsets can be very long if the cut-off frequency is low (1Hz or less). This
settling time can be impractical. For example, it can delay the measurement for
several seconds after making contact with the subject. This situation repeats
every time contact is lost or the electrodes move slightly due to motion
artifacts.
If Fast Restore is enabled (via a digital input), the Fast Restore circuit
automatically detects when the signal is lost and momentarily increases the
corner frequency of the high pass, thus making the settling time much shorter.
This is achieved by switching in a small resistor in parallel with the high
value external resistor.
It is important to note the part automatically switches back to normal once the
signal is settled and that this feature performs automatically without the
intervention of the processor.