DRV8821_16 Datasheet, PDF (15/32 Pages) Texas Instruments – Dual Stepper Motor Controller and Driver

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Device Functional Modes (continued)
VM
DRV8821
SLVS912J – JANUARY 2009 – REVISED JANUARY 2016
1
xOUT1
3
2
xOUT2
1 Drive current
2 Fast decay (reverse)
3 Slow decay (brake)
Figure 11. Decay Mode
The DRV8821 also supports a mixed decay mode. Mixed decay mode begins as fast decay, but after a period of
time (75% of the PWM cycle) switches to slow decay mode for the remainder of the fixed PWM period.
Mixed decay mode is only active if the current through the winding is decreasing (per the indexer step table); if
the current is increasing, then slow decay is always used.
Slow or mixed decay mode is selected by the state of the xDECAY pins - logic low selects slow decay, and logic
high selects mixed decay operation.
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