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TMC4670 Datasheet PRELIMINARY • IC Version V0.99 | Document Revision V0.91 • 2016-Nov-09
The ADC_UX, ADC_V, ADC_WY are for the FOC3 (U, V, W). The ADC_UX. and ADC_WY (X, Y) are for the FOC2.
Note
The Open Loop Encoder is useful for setup of ADC channel selection, scaling, and
offset by turning a motor open loop.
3.6 Encoder Engine
The encoder engine is an unified position sensor interface. It maps the selected encoder position informa-
tion to electrical position (phi_e) and to mechanical position (phi_e) the electrical angle. Both are 16 bit
values. The encoder engine maps single turn positions from position sensors to multi-turn position. The
user can overwrite the these multi-turn position for initialization.
The different position sensors are the position sources for torque and flux control via FOC, for velocity
control, and for position control. The PHI_E_SELECTION selects the source of the electrical angel phi_e
for the inner FOC control loop. VELOCITY_SELECTION selects the source for velocity measurement. With
phi_e selected as source for velocity measurement, one gets the electrical velocity. With the mechanical
angle phi_m selected as source for velocity measurement one gets the mechanical velocity taking the set
number of pole pairs (N_POLE_PAIRS) of the motor into account. Nevertheless, for high precision position
it might be useful to do positioning based on the electrical angel phi_e.
3.6.1 Open Loop Encoder
For initial system setup the encoder engine is equipped with an open loop position generator. With one
can turn the motor open-loop by specifying speed in rpm and acceleration in rpm/s together with a voltage
UD_EXT in D direction. So, the open-loop encoder it is not a real encoder, it just gives positions as an
encoder does. The open-loop decoder has a direction bit to define once the direction of motion for the
application.
Note
The open loop encoder is useful for initial ADC setup, encoder setup, hall signal
validation, and for validation of the number of pole pairs of a motor. The open
loop encoder turns a motor open with programmable velocity in unit [RPM] with
programmable acceleration in unit [RPM/s].
So, with the open loop encoder one can turn a motor without any position sensor and without any current
measurement as the first step of doing the system setup. With the turning motor one can adjust the ADC
scales and offsets and set up positions sensors (hall, incremental encoder, . . . ) according to resolution,
orientation, direction of rotation.
3.6.2 Incremental ABN Encoder
The incremental encoders give two phase shifted incremental pulse signals A and B. Some incremental
encoders have an additional null position signal N or zero pulse signal Z. An incremental encoder (called
ABN encoder or ABZ encoder) has an individual number of incremental pulses per revolution. The number
of incremental pulses define the number of positions per revolution (PPR). The PPR might mean pulses
per revolution or periods per revolution. Instead of positions per revolution some incremental encoder
vendors call these CPR counts per revolution.
The PPR parameter is the most important parameter of the incremental encoder interface. With that, it
forms a modulo (PPR) counter, counting from 0 to (PPR-1). Depending on the direction, it counts up or
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