L6470PD datasheet(23/70 Pages) STMICROELECTRONICS

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L6470

Functional description

Doc ID16737 Rev 5

23/70

6.4.1

Automatic full-step mode

When motor speed is greater than a programmable full-step speed threshold, the L6470

switches automatically to Full-step mode (see Figure 7); the driving mode returns to

microstepping when motor speed decreases below the full-step speed threshold. The full-

step speed threshold is set through the FS_SPD register (see Section 9.1.9).

Figure 7.

Automatic full-step switching

6.5

Absolute position counter

An internal 22-bit register (ABS_POS) records the motor motion according to the selected

step mode; the stored value unit is equal to the selected step mode (full, half, quarter, etc.).

The position range is from -221to +221-1 (µ)steps (see Section 9.1.1).

6.6

Programmable speed profiles

The user can easily program a customized speed profile defining independently

acceleration, deceleration, maximum and minimum speed values by the ACC, DEC,

MAX_SPEED and MIN_SPEED registers respectively (see Section 9.1.5, 9.1.6, 9.1.7 and

9.1.8).

When a command is sent to the device, the integrated logic generates the microstep

frequency profile that performs a motor motion compliant to speed profile boundaries.

All acceleration parameters are expressed in step/tick2 and all speed parameters are

expressed in step/tick; the unit of measurement does not depend on the selected step

mode. Acceleration and deceleration parameters range from 2-40 to (212-2)•2-40 step/tick2

(equivalent to 14.55 to 59590 step/s2).

The minimum speed parameter ranges from 0 to (212-1)•2-24 step/tick (equivalent to 0 to

976.3 step/s).

The maximum speed parameter ranges from 2-18 to (210-1)• 2-18 step/tick (equivalent to

15.25 to 15610 step/s).

Phase A

Phase B

(2N+1) x

π/4

(2N+1) x

π/4

Full-Step

μStepping

peak

sin(

π/4) x I

peak

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