L6472 datasheet(44/69 Pages) STMICROELECTRONICS

44 / 69 page

Programming manual

L6472

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Doc ID 022729 Rev 1

9.1.9

FS_SPD

The FS_SPD register contains the threshold speed. When the actual speed exceeds this

value the step mode is automatically switched to full-step two-phase on. Its value is

expressed in step/tick (format unsigned fixed point 0.18) and to convert it in step/s the

following formula can be used.

Equation 6

If the FS_SPD value is set to hFF (max.) the system always works in microstepping mode

(SPEED must go beyond the threshold to switch to full-step mode). Setting FS_SPD to zero

does not have the same effect as setting step mode to full-step two phase on: the zero

FS_SPD value is equivalent to a speed threshold of about 7.63 step/s.

The available range is from 7.63 to 15625 step/s with a resolution of 15.25 step/s.

9.1.10

TVAL_HOLD, TVAL_RUN, TVAL_ACC and TVAL_DEC

The TVAL_HOLD register contains the current value that is assigned to the torque

regulation DAC when the motor is stopped.

The TVAL_RUN register contains the current value that is assigned to the torque regulation

DAC when the motor is running at constant speed.

The TVAL_ACC register contains the current value that is assigned to the torque regulation

DAC during acceleration.

The TVAL_DEC register contains the current value that is assigned to the torque regulation

DAC during deceleration.

The available range is from 31.25 mA to 4 A with a resolution of 31.25 mA, as shown in

Table 12.

step

⁄

[]

FSSPD

0.5

() 2

–

⋅

tick

-----------------------------------------------------------

Table 12.

Torque regulation by TVAL_HOLD, TVAL_ACC, TVAL_DEC and

TVAL_RUN registers

TVAL_X [6..0]

Output current amplitude

31.25 mA

62.5 mA

3.969 A

4 A

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