Function description and application information

SPMD150STP

18/23

Doc ID 17160 Rev 1

The clock pulse, with the HALF/FULL input high, advances the state machine from state 1 to

either state 2 or 8 depending on the CW/CCW input.

Starting from this point, keeping the HALF/FULL input low, the state machine will advance

following the sequence 2,4,6,8,… if CW/CCW is high (Clockwise movement) or 8,6,4,2,… if

CW/ CCW is low (Counterclockwise movement).

Figure 19.

Wave drive mode

4.5.4

Microstepping

STMD150STP has two separate control current loop, with the possibility to set the current

level in an independent way (by means VREFA and VREFB); this feature make possible the

actuation of the micro-stepping mode.

Micro-stepping mode is a full step mode performed with a not fixed current in the motor

phases, but with a current varying in a sinusoidal mode;

that means the current flowing in the motor is not a square wave, but a sinusoidal wave.

Main commands remain the same, but during the period of each clock step, VREFA and

VREFB are incremented or decremented through a defined number of level, this number

gives the name to the micro-stepping granularity;

as example, a 64 micro-step per step means that, for each “standard” step there are 64 step

values on VREFA/B (from zero to VREFA/B max and from VREFB/A max to zero, see

Figure 20)