Texas Instruments DRV8886AT, User Manual

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1.232 VRREF _ R
I Device _ Full _ Scale TORQUE StepModifier
1.232
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Introduction
5 SLVUB16 – February 2017
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Copyright © 2017, Texas Instruments Incorporated
DRV8886AT Evaluation Module User's Guide
The current is calculated using the VREF slider, the sense resistor value, the torque setting, and the
step mode setting using
Equation 1 .
where
• StepModifier is 0.71 for full step and 1 for other STEP MODE settings (1)
The number 1.232 is based on the maximum current allowed using the configuration. If VRREF = 0 V,
the maximum current is 1 A. The 12-bit DAC channel 1 is connected to the DRV8886AT analog input
RREF through a 15-k
Ω series resistor. The DAC voltage begins at 1.232 V (0%) and ends at 0 V
(100%).
Step 8. After setting up the control signals for the DRV8886AT, select both the WAKE and ENABLE
toggle buttons to enable the DRV8886AT. When toggled, the WAKE or ENABLE status
toggles between red and green.
The WAKE toggle button, which controls the nSLEEP pin, is used to wake the DRV8886AT. The
ENABLE toggle button, which controls the ENABLE pin, is used to enable the DRV8886AT outputs.
A message stating Both WAKE and ENABLE must be green to enable the motor control buttons is
visible until both the WAKE and ENABLE toggle buttons are activated. When these two toggle buttons
have been activated, the message disappears and the
Start/Stop Steps and Move # of Steps toggle
buttons are available.
If the WAKE or ENABLE toggle buttons are selected during motor operation, the motor is immediately
stopped and the STEP control signal from the microcontroller is reset.
Figure 4. Wake and Enable Toggle Buttons
Step 9. The DRV8886AT EVM is now awake and can be commanded to turn the motor. Turning the
motor occurs by either selecting the
Start/Stop Steps , Move # of Steps , or Reciprocate toggle
button.
The Start/Stop Steps toggle button is used to run the motor indefinitely. The motor will accelerate to the
target speed and run until the Start/Stop Steps toggle button is selected. When the Start/Stop Steps toggle
button is selected, the red button changes to green, and the Move Steps and Reciprocate toggle buttons
are disabled.