Sampling Rate
It states how many times per second the driver reads the analogue reference and the current feedback. A 1 kHz sampling rate means an average delay of 0.5 ms, and 1 ms in the worst case, for a change at the input to reach the output. In functions such as current-sensing stop, this delay adds directly to the response time.
The microcontroller does not measure continuously but at defined intervals. The time between each reading is the lower bound on how quickly the system can respond to an event.
- Speed reference: The operator turning a pot happens on the scale of seconds; sampling between 100 Hz and 1 kHz is more than enough.
- Current protection: Stall current climbs within milliseconds. In an AntiSwitch type current-sensing stop, if sampling is slow the mechanism keeps straining until the threshold is caught.
- Averaging: To suppress PWM switching noise the driver generally takes the average of several successive samples; this improves stability while delaying the response by as many samples.
The moment of sampling matters too: if the current reading is taken in the middle of the PWM pulse the real current is read, if taken at its edge the switching noise is read. That is why the measurement is mostly synchronised with the PWM signal.
If you come across a current threshold that triggers early or late in the field, keep in mind that the problem may stem not from the threshold value but from the moment at which the measurement is taken.
Context where this term is used: DC Motor Driver Selection Guide