DRV8711_15 Datasheet, PDF (29/44 Pages) Texas Instruments – DRV8711 Stepper Motor Controller IC

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8 Applications and Implementation
DRV8711
SLVSC40E – JUNE 2013 – REVISED MARCH 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The DRV8711 is used in bipolar stepper control. The microstepping motor predriver provides additional precision
and a smooth rotation from the stepper motor.
8.1.1 Sense Resistor
For optimal performance, it is important for the sense resistor to be:
• Surface-mount
• Low inductance
• Rated for high enough power
• Placed closely to the motor driver
The power dissipated by the sense resistor equals I_RMS2 × R. For example, if peak motor current is 3 A, RMS
motor current is 2 A, and a 0.05-Ω sense resistor is used, the resistor will dissipate 2 A² × 0.05 Ω = 0.2 W. The
power quickly increases with higher current levels.
Resistors typically have a rated power within some ambient temperature range, along with a derated power curve
for high ambient temperatures. When a PCB is shared with other components generating heat, margin should be
added. It is always best to measure the actual sense resistor temperature in a final system, along with the power
MOSFETs, as those are often the hottest components.
Because power resistors are larger and more expensive than standard resistors, it is common practice to use
multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat
dissipation.
8.1.2 Optional Series Gate Resistor
In high current or high voltage applications, the low side predriver fault may assert due to noise in the system. In
this application, TI recommends placing a 47 to 120-Ω resistor in series with the low side output and the gate of
the low side FET. TI also recommends setting the dead time to 850 ns when adding a series resistor.
8.2 Typical Application
The following design is a common application of the DRV8711.
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