current Smaract motors parameters : 
- Closed loop Max frequency : 5000
- Signal Amplitude threshold : 2047
- High voltage threshold : 511

when one drives the Smaract motors in "closed loop" mode, one can get a displacement as small as 50nm... but at the price of a delock of the laser/FP-cavity.

when one drives the motor in "open loop" mode, 1 step is equivalent to 4µm !!! it is much larger than the laser PZT range.

when one drives the motor in "Piezo Scan" mode with a speed of 1V/s, one can move the motor without losing the laser/Fp-cavity lock.
the PZT voltage range of 100V (max value) is roughly equivalent to 2-3µm of round trip length, which is enough to manage several "fast" (10-20 minutes) oscillations of the laser frequency :
see these posts to get some info on the laser frequency oscillations : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/289