TMC5161 DATASHEET (Rev. 1.01 / 2018-NOV-20)
106
21 DC Motor or Solenoid
The TMC5161 can drive one or two DC motors using one coil output per DC motor. Either a torque
limited operation, or a voltage based velocity control with optional torque limit is possible.
CONFIGURATION AND CONTROL
Set the flag direct_mode in the GCONF register. In direct mode, the coil current polarity and coil
current, respectively the PWM duty cycle become controlled by register XTARGET (0x2D). Bits 8..0
control motor A and Bits 24..16 control motor B PWM. Additionally to this setting, the current limit is
scaled by IHOLD. The STEP/DIR inputs and the motion controller are not used in this mode.
PWM DUTY CYCLE VELOCITY CONTROL
In order to operate the motor at different velocities, use the stealthChop voltage PWM mode in the
following configuration:
en_pwm_mode = 1, pwm_autoscale = 0, PWM_OFS = 255, PWM_GRAD = 4, IHOLD = 31
Set TOFF > 0 to enable the driver.
In this mode the driver behaves like a 4-quadrant power supply. The direct mode setting of PWM A
and PWM B using XTARGET controls motor voltage, and thus the motor velocity. Setting the
corresponding PWM bits between -255 and +255 (signed, two’s complement numbers) will vary motor
voltage from -100% to 100%. With pwm_autoscale = 0, current sensing is not used and the sense
resistors should be eliminated or 150mΩ or less to avoid excessive voltage drop when the motor
becomes heavily loaded up to 2.5A. Especially for higher current motors, make sure to slowly
accelerate and decelerate the motor in order to avoid overcurrent or triggering driver overcurrent
detection.
To activate optional motor freewheeling, set IHOLD = 0 and FREEWHEEL = %01.
ADDITIONAL TORQUE LIMIT
In order to additionally take advantage of the motor current limitation (and thus torque controlled
operation) in stealthChop mode, use automatic current scaling (pwm_autoscale = 1). The actual current
limit is given by IHOLD and scaled by the respective motor PWM amplitude, e.g. PWM = 128 yields in
50% motor velocity and 50% of the current limit set by IHOLD. In case two DC motors are driven in
voltage PWM mode, note that the automatic current regulation will work only for the motor which
has the higher absolute PWM setting. The PWM of the second motor also will be scaled down in case
the motor with higher PWM setting reaches its current limitation.
PURELY TORQUE LIMITED OPERATION
For a purely torque limited operation of one or two motors, spread cycle chopper individually
regulates motor current for both full bridge motor outputs. When using spreadCycle, the upper motor
velocity is limited by the supply voltage only (or as determined by the load on the motor).
21.1 Solenoid Operation
The same way, one or two solenoids (i.e. magnetic coil actuators) can be operated using spreadCycle
chopper. For solenoids, it is often desired to have an increased current for a short time after
switching on, and reduce the current once the magnetic element has switched. This is automatically
possible by taking advantage of the automatic current scaling (IRUN, IHOLD, IHOLDDELAY and
TPOWERDOWN). The current scaling in direct_mode is still active, but will not be triggered if no step
impulse is supplied. Therefore, a step impulse must be given to the STEP input whenever one of the
coils shall be switched on. This will increase the current for both coils at the same time.
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