Datasheet

DocID16737 Rev 7 23/73
L6470 Functional description
73
Automatic full-step mode
When motor speed is greater than a programmable full-step speed threshold, the L6470
device 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 on page 44).
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 -2
21
to +2
21
-1 (µ)steps (see Section 9.1.1 on page 41).
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 on page 42,
Section 9.1.6 on page 43, Section 9.1.7 on page 43 and Section 9.1.8 on page 43).
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/tick
2
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 (2
12
- 2) 2
-40
step/tick
2
(equivalent to 14.55 to 59590 step/s
2
).
The minimum speed parameter ranges from 0 to (2
12
-
1
) 2
-24
step/tick (equivalent to 0 to
976.3 step/s).
The maximum speed parameter ranges from 2
-18
to (2
10
- 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
μStepping
I
peak
sin(π/4) x I
peak