TMC5130A DATASHEET (Rev. 1.14 / 2017-MAY-15)
88
17.2 Changing Resolution
A reduced microstep resolution allows limitation of the step frequency for the STEP/DIR interface, or
compatibility to an older, less performing driver. The internal microstep table with 1024 sine wave
entries generates sinusoidal motor coil currents. These 1024 entries correspond to one electrical
revolution or four fullsteps. The microstep resolution setting determines the step width taken within
the table. Depending on the DIR input, the microstep counter is increased (DIR=0) or decreased
(DIR=1) with each STEP pulse by the step width. The microstep resolution determines the increment
respectively the decrement. At maximum resolution, the sequencer advances one step for each step
pulse. At half resolution, it advances two steps. Increment is up to 256 steps for fullstepping. The
sequencer has special provision to allow seamless switching between different microstep rates at any
time. When switching to a lower microstep resolution, it calculates the nearest step within the target
resolution and reads the current vector at that position. This behavior especially is important for low
resolutions like fullstep and halfstep, because any failure in the step sequence would lead to
asymmetrical run when comparing a motor running clockwise and counterclockwise.
EXAMPLES:
Fullstep:
Cycles through table positions: 128, 384, 640 and 896 (45°, 135°, 225° and 315° electrical
position, both coils on at identical current). The coil current in each position
corresponds to the RMS-Value (0.71 * amplitude). Step size is 256 (90° electrical)
Half step:
The first table position is 64 (22.5° electrical), Step size is 128 (45° steps)
Quarter step: The first table position is 32 (90°/8=11.25° electrical), Step size is 64 (22.5° steps)
This way equidistant steps result and they are identical in both rotation directions. Some older drivers
also use zero current (table entry 0, 0°) as well as full current (90°) within the step tables. This kind of
stepping is avoided because it provides less torque and has a worse power dissipation in driver and
motor.
Step position
table position
64
current coil A
38.3%
current coil B
92.4%
Half step 0
Full step 0
Half step 1
Half step 2
Full step 1
Half step 3
Half step 4
Full step 2
Half step 5
Half step 6
Full step 3
Half step 7
128
192
320
384
448
576
640
704
832
896
960
70.7%
92.4%
92.4%
70.7%
38.3%
-38.3%
-70.7%
-92.4%
-92.4%
-70.7%
-38.3%
70.7%
38.3%
-38.3%
-70.7%
-92.4%
-92.4%
-70.7%
-38.3%
38.3%
70.7%
92.4%
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
