DRV8824_16 Datasheet, PDF (13/35 Pages) Texas Instruments – Stepper Motor Controller IC

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Feature Description (continued)
DRV8824
SLVSA06J – OCTOBER 2009 – REVISED JULY 2014
Figure 7. Decay Mode
The DRV8824 supports fast decay, slow decay, and a mixed decay mode. Slow, fast, or mixed decay mode is
selected by the state of the DECAY pin – logic low selects slow decay, open selects mixed decay operation, and
logic high sets fast decay mode. The DECAY pin has both an internal pullup resistor of approximately 130 kΩ
and an internal pulldown resistor of approximately 80 kΩ. This sets the mixed decay mode if the pin is left open
or undriven.
Mixed decay mode begins as fast decay, but at a fixed period of time (75% of the PWM cycle) switches to slow
decay mode for the remainder of the fixed PWM period. This occurs only if the current through the winding is
decreasing (per Table 2); if the current is increasing, then slow decay is used.
8.3.4 Blanking Time
After the current is enabled in an H-bridge, the voltage on the xISEN pin is ignored for a fixed period of time
before enabling the current sense circuitry. This blanking time is fixed at 3.75 μs. Note that the blanking time also
sets the minimum on time of the PWM.
8.3.5 Microstepping Indexer
Built-in indexer logic in the DRV8824 allows a number of different stepping configurations. The MODE0 through
MODE2 pins are used to configure the stepping format, as shown in Table 1.
MODE2
0
0
0
0
1
1
1
1
MODE1
0
0
1
1
0
0
1
1
Table 1. Stepping Format
MODE0
0
1
0
1
0
1
0
1
STEP MODE
Full step (2-phase excitation) with 71% current
1/2 step (1-2 phase excitation)
1/4 step (W1-2 phase excitation)
8 microsteps/step
16 microsteps/step
32 microsteps/step
32 microsteps/step
32 microsteps/step
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