L6470PD datasheet(44/70 Pages) STMICROELECTRONICS

44 / 70 page

Programming manual

L6470

44/70

Doc ID16737 Rev 5

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

following formula can be used.

Equation 9

If the FS_SPD value is set to h3FF (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

KVAL_HOLD, KVAL_RUN, KVAL_ACC and KVAL_DEC

The KVAL_HOLD register contains the KVAL value that is assigned to the PWM modulators

when the motor is stopped (compensation excluded).

The KVAL_RUN register contains the KVAL value that is assigned to the PWM modulators

when the motor is running at constant speed (compensation excluded).

The KVAL_ACC register contains the starting KVAL value that can be assigned to the PWM

modulators during acceleration (compensation excluded).

The KVAL_DEC register contains the starting KVAL value that can be assigned to the PWM

modulators during deceleration (compensation excluded).

The available range is from 0 to 0.996 x VS with a resolution of 0.004 x VS, as shown in

Table 12.

9.1.11

INT_SPEED

The INT_SPEED register contains the speed value at which the BEMF compensation curve

changes slope (see Section 7.4). Its value is expressed in step/tick and to convert it in

step/s, the following formula can be used:

Equation 10

where INT_SPEED is the integer number stored in the register and tick is 250 ns.

step/s

[]

FS_SPD

0.5

() 2

–

⋅

tick

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

Table 12.

Voltage amplitude regulation registers

KVAL_X [7..0]

Output voltage

00000

000

00000

001

VS x (1/256)

11111

110

VS x (254/256)

11111

111

VS x (255/256)

step

⁄

[]

INT SPEED

–

⋅

tick

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