Datasheet

TMC4671 Datasheet • IC Version V1.3 | Document Revision V2.00 • 2020-Apr-17
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The goal of the initialization of an incremental encoder is to set it up so that the magnetic axis of the rotor
fits with the electrical angle phi_e with the angle zero on D axis. For this, one needs to know the number of
pole pairs NPP, the resolution of the incremental encoder in pulses per revolution PPR, and the orientation
between measured encoder angle of the rotor and the electrical angle of the field orientation. An encoder
measures mechanical angle phi_m were the FOC needs the electrical angle phi_e for commutation. The
number of pole pairs NPP determines the ratio between mechanical angle phi_m and electrical angle phi_e.
The parameters phi_m_offset and phi_e_offset are for compensation of differences in orientation angle by
adjustments.
Figure 21: ABN Incremental Encoder N Pulse
The N pulse from an encoder triggers either sampling of the actual encoder count to fetch the position at
the N pulse or it re-writes the fetched n position on an N pulse. The N pulse can either be used as stand
alone pulse or and-ed with NAB = N and A and B. It depends on the decoder what kind of N pulse has to be
used - either N or NAB. For those encoders with precise N pulse within one AB quadrant, the N pulse must
be used. For those encoders with N pulse over four AB quadrants the user can enhance the precision of
the N pulse position detection by using NAB instead of N.
Note
Incremental encoders are available with N pulse and without N pulse.
The polarity of N pulse, A pulse and B pulse are programmable. The N pulse is for re-initialization with
each turn of the motor. Once fetched, the ABN decoder can be configured to write back the fetched N
pulse position with each N pulse.
Note
The ABN encoder interface has a direction bit to set to match wiring of motor to
direction of encoder.
Logical ABN = A and B and N might be useful for incremental encoders with low resolution N pulse to
enhance the resolution. On the other hand, for incremental encoders with high resolution N pulse a logical
ABN = A and B and N might totally suppress the resulting N pulse.
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