TMC5130A DATASHEET (Rev. 1.14 / 2017-MAY-15)
70
CHOICE OF RREF FOR OPERATION WITHOUT SENSE RESISTORS
RREF [Ω]
Peak current [A]
(CS=31, vsense=0)
Peak current [A]
(CS=31, vsense=1)
6k8
7k5
8k2
9k1
10k
12k
15k
18k
22k
27k
33k
1.92
1.76
1.63
1.49
1.36
1.15
0.94
0.79
0.65
0.60
0.54
1.06
0.97
0.90
0.82
0.75
0.63
0.52
0.43
0.36
0.33
0.29
In RDSon measurement mode, connect the BRA and BRB pins to GND using the shortest possible path
(i.e. lowest possible PCB resistance). In a realistic setup, the effective current will be slightly lower
than expected. RDSon based measurement gives best results when combined with classic constant off
time chopper or with the voltage PWM stealthChop. When using spreadCycle with RDSon based
current measurement, slightly asymmetric current measurement for positive currents (on phase) and
negative currents (fast decay phase) can result in chopper noise. This especially occurs at increased
die temperature and increased motor current.
Note
The absolute current levels achieved with RDSon based current sensing may depend on PCB layout
exactly like with external sense resistors, because trace resistance on BR pins will add to the effective
sense resistance. Therefore we recommend to measure and calibrate the current setting within the
application.
Thumb rule
RDSon based current sensing works best for motors with up to 1.2A RMS current. The best results are
yielded with stealthChop operation in combination with RDSon based current sensing. Consider using
classic chopper rather than spreadCycle.
For most precise current control and best results with spreadCycle, it is recommended to use external
1% sense resistors rather than RDSon based current control.
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
