DRV8880_15 Datasheet, PDF (22/48 Pages) Texas Instruments – DRV8880 2-A Stepper Motor Driver With AutoTune™

DRV8880
SLVSD18A – JUNE 2015 – REVISED JULY 2015
7.3.5.2 Mode 2: Slow Decay for Increasing Current, Mixed Decay for Decreasing current
I_TRIP
www.ti.com
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
tOFF
tBLANK
tDRIVE
I_TRIP
tBLANK
tDRIVE
tFAST
tOFF
tBLANK
tDRIVE
tFAST
tOFF
Figure 17. Slow/Mixed Decay Mode
Mixed decay begins as fast decay for a time, followed by slow decay for the remainder of t_OFF. In this mode,
mixed decay only occurs during decreasing current. Slow decay is used for increasing current.
This mode exhibits the same current ripple as slow decay for increasing current, since for increasing current, only
slow decay is used. For decreasing current, the ripple is larger than slow decay, but smaller than fast decay. On
decreasing current steps, mixed decay will settle to the new I_TRIP level faster than slow decay.
In cases where current is held for a long time (no input in the STEP pin) or at very low stepping speeds, slow
decay may not properly regulate current because no back-EMF is present across the motor windings. In this
state, motor current can rise very quickly, and may require a large off-time. In some cases this may cause a loss
of current regulation, and a more aggressive decay mode is recommended.
22
Submit Documentation Feedback
Product Folder Links: DRV8880
Copyright © 2015, Texas Instruments Incorporated