Datasheet

TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.03 • 2018-Sept-06
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Hexadecimal Value u16 s16 q8.8 q4.12
0x5A81
h
23169 23169 23169 / 256 23169 / 4096
0x7FFF
h
32767 32767 32767 / 256 32767 / 4096
0x8000
h
32768 -32768 -32768 / 256 -32768 / 4096
0x8001
h
32769 -32767 -32767 / 256 -32767 / 4096
0x8002
h
32770 -32766 -32766 / 256 -32766 / 4096
0xC001
h
49153 -16383 -16383 / 256 -16383 / 4096
0xFFFE
h
65534 -2 -2 / 256 -2 / 4096
0xFFFF
h
65535 -1 -1 / 256 -1 / 4096
Table 5: Examples of u16, s16, q8.8, q4.12
The q8.8 and q4.12 are used for P and I parameters which are positive numbers. Note that q8.8 and q4.12
are used as signed numbers. This is because theses values are multiplied with signed error values resp.
error integral values.
4.3.2 N_POLE_PAIRS, PHI_E, PHI_M
The parameter N_POLE_PAIRS defines the factor between electrical angle PHI_E and mechanical angle
PHI_M of a motor (pls. refer figure 12).
A motor with one (1) pole pair turns once for each electrical period. A motor with two (2) pole pairs turns
once for every two electrical periods. A motor with three (3) pole pairs turns once for every three electrical
periods. A motor with four pole (4) pairs turns once for every four electrical periods.
The electrical angle PHI_E is relevant for the commutation of the motor. It is relevant for the torque control
of the inner FOC loop.
PHI_E = PHI_M · N_POLE_PAIRS (3)
The mechanical angle PHI_M is primarily relevant for velocity control and for positioning. This is because
one wants to control the motor speed in terms of mechanical turns and not in terms of electrical turns.
PHI_M = PHI_E/N_POLE_PAIRS (4)
Different encoders give different kinds of position angles. Digital Hall sensors normally give the electrical
position PHI_E that can be used for commutation. Analog encoders give - depending on their resolu-
tion - angles that have to be scaled first to mechanical angles PHI_M and to electrical angles PHI_E for
commutation.
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