DRV8886AT Datasheet, PDF (22/40 Pages) Texas Instruments – 2-A Stepper Motor Driver With Integrated Current Sense and AutoTune Technology

DRV8886AT
SLVSDO1 – JANUARY 2017
www.ti.com
7.3.6.3 Mode 3: AutoTune Ripple Control
The AutoTune current regulation schemes are advanced current-regulation control methods that use additional
components as compared to traditional fixed off-time current regulation schemes. AutoTune current regulation
schemes help the stepper motor driver adjust the decay scheme based on operating factors such as the ones
listed as follows:
• Motor winding resistance and inductance
• Motor aging effects
• Motor dynamic speed and load
• Motor supply voltage variation
• Motor back-EMF difference on rising and falling steps
• Step transitions
• Low-current versus high-current dI/dt
The DRV8886AT device provides two different AutoTune current regulation modes, named AutoTune Ripple
Control and AutoTune Dynamic Decay.
I_TRIP
I_VALLEY
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
I_TRIP
I_VALLEY
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
tOFF
Figure 20. AutoTune Ripple Control Decay Mode
AutoTune Ripple Control operates by setting an I_VALLEY level alongside the I_TRIP level. When the current level
reaches I_TRIP, instead of entering slow decay until the t_OFF time expires, the driver enters slow decay until I_VALLEY
is reached. Slow decay operates similar to mode 1 in which both low-side MOSFETs are turned on allowing the
current to recirculate. In this mode, t_OFF varies depending on the current level and operating conditions.
This method allows much tighter regulation of the current level increasing motor efficiency and system
performance. AutoTune Ripple Control can be used in systems that can tolerate a variable off-time regulation
scheme to achieve small current ripple in the current regulation.
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