DRV8846_15 Datasheet, PDF (19/35 Pages) Texas Instruments – DRV8846 Dual H-Bridge Stepper Motor Driver

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DRV8846
SLLSEK2 – JUNE 2014
Figure 9 shows increasing and decreasing current. When current is decreasing, the decay mode used is fast,
slow, or mixed as commanded by the DEC1 and DEC0 pins. Three DEC pin selections allow for mixed decay
during increasing current.
Increasing Decreasing
Increasing Decreasing
STEP Input
Decreasing
Increasing Decreasing
Increasing
STEP Input
Figure 9. Increasing and Decreasing Current
Adaptive decay mode simplifies the decay mode selection by dynamically changing to adjust for current level,
step change, supply variation, BEMF, and load. To enable adaptive decay mode, pull the ADEC pin to logic high
and pull DEC0 and DEC1 pins to logic high. The state of the ADEC pin is only evaluated when exiting sleep
mode.
Adaptive decay adjusts the time spent in fast decay to minimize current ripple and quickly adjust to current-step
changes. If the drive time is longer than the minimum (t_BLANK), in order to reach the current trip point, the decay
mode applied is slow decay (see Figure 10).
Iref
tBLANK
tON
tOFF (fixed)
tBLANK
tON
tOFF (fixed)
tBLANK
tON
tOFF (fixed)
FET Drive On (FWD or REV)
Slow Decay
Figure 10. Adaptive Decay – Slow Decay Operation
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