DRV8880_15 Datasheet, PDF (14/48 Pages) Texas Instruments – DRV8880 2-A Stepper Motor Driver With AutoTune™

DRV8880
SLVSD18A – JUNE 2015 – REVISED JULY 2015
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7.3 Feature Description
7.3.1 Stepper Motor Driver Current Ratings
Stepper motor drivers can be classified using three different numbers to describe the output current: peak, rms,
and full-scale.
7.3.1.1 Peak Current Rating
The peak current in a stepper driver is limited by the overcurrent protection trip threshold I_OCP. The peak current
describes any transient duration current pulse, for example when charging capacitance, when the overall duty
cycle is very low. In general the minimum value of I_OCP specifies the peak current rating of the stepper motor
driver. For the DRV8880, the peak current rating is 2.5 A per bridge.
7.3.1.2 RMS Current Rating
The rms (average) current is determined by the thermal considerations of the IC. The rms current is calculated
based on the R_DS(ON), rise and fall time, PWM frequency, device quiescent current, and package thermal
performance in a typical system at 25°C. The real operating rms current may be higher or lower depending on
heatsinking and ambient temperature. For the DRV8880, the rms current rating is 1.4 A per bridge.
7.3.1.3 Full-Scale Current Rating
The full-scale current describes the top of the sinusoid current waveform while microstepping. Since the
sineusoid amplitude is related to the rms current, the full-scale current is also determined by the thermal
considerations of the IC. The full-scale current rating is approximately √2 × I_rms. The full-scale current is set by
VREF, the sense resistor, and Torque DAC when configuring the DRV8880 , see Current Regulation for details.
For the DRV8880, the full-scale current rating is 2.0 A per bridge.
Full-scale current
RMS current
AOUT
BOUT
Step Input
Figure 12. Full-Scale and rms Current
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