Datasheet

TMC220X, TMC222X DATASHEET (Rev. 1.02 / 2017-MAY-16) 45
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6.6.2 PWM_SCALE_SUM Informs about the Motor State
Information about the motor state is available with automatic scaling by reading out
PWM_SCALE_SUM. As this parameter reflects the actual voltage required to drive the target current into
the motor, it depends on several factors: motor load, coil resistance, supply voltage, and current
setting. Therefore, an evaluation of the PWM_SCALE_SUM value allows checking the motor operation
point. When reaching the limit (255), the current regulator cannot sustain the full motor current, e.g.
due to a drop in supply volage.
6.7 Freewheeling and Passive Braking
stealthChop provides different options for motor standstill. These options can be enabled by setting
the standstill current IHOLD to zero and choosing the desired option using the FREEWHEEL setting.
The desired option becomes enabled after a time period specified by TPOWERDOWN and
IHOLD_DELAY. Current regulation becomes frozen once the motor target current is at zero current in
order to ensure a quick startup. With the freewheeling options, both freewheeling and passive
braking can be realized. Passive braking is an effective eddy current motor braking, which consumes a
minimum of energy, because no active current is driven into the coils. However, passive braking will
allow slow turning of the motor when a continuous torque is applied.
Hint
Operate the motor within your application when exploring stealthChop. Motor performance often is
better with a mechanical load, because it prevents the motor from stalling due mechanical oscillations
which can occur without load.
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