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TMC4670 Datasheet PRELIMINARY • IC Version V0.99 | Document Revision V0.91 • 2016-Nov-09
the smallest negative number
−
2(n−1) might cause critical under-flow or over-flow. Internal clipping takes
this into account by mapping −2(n−1) to −2(n−1) + 1.
Hexadecimal Value
0x0000h
0x0001h
0x0001h
0x0080h
0x0100h
0x0200h
0x3FFFh
u16
0
s16
0
q8.8
0.0
q4.12
0.0
1
1
1 / 256
2 / 256
0.5
1 / 4096
2
2
2 / 4096
128
256
512
16383
23169
32767
128
256
512
16383
23169
32767
0.03125
1.0
0.0625
2.0
0.125
16383 / 256
23169 / 256
32767 / 256
16383 / 4096
23169 / 4096
32767 / 4096
0x5A81h
0x7FFFh
0x8000h
0x8001h
0x8002h
0xC001h
0xFFFEh
32768 -32768 -32768 / 256 -32768 / 4096
32769 -32767 -32767 / 256 -32767 / 4096
32770 -32766 -32766 / 256 -32766 / 4096
49153 -16383 -16383 / 256 -16383 / 4096
65534
65535
-2
-1
-2 / 256
-1 / 256
-2 / 4096
-1 / 4096
0xFFFFh
Table 4: 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 but 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.
3.4.2 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 5).
A motor with one (1) pole pair turns once for each electrical period. A motor with two (2) pole pairs turns
once for each two electrical periods. A motor with three (3) pole pairs turns once for each three electrical
periods. A motor with four pole (4) pairs turns once for each 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
(1)
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.
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