DRV8886AT Datasheet, PDF (13/40 Pages) Texas Instruments – 2-A Stepper Motor Driver With Integrated Current Sense and AutoTune Technology

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DRV8886AT
SLVSDO1 – JANUARY 2017
7.3 Feature Description
Table 1 lists the recommended external components for the DRV8886AT device.
Table 1. DRV8886AT External Components
COMPONENT
C_VM1
C_VM2
C_VCP
C_SW
C_AVDD
C_DVDD
R_nFAULT
R_REF
PIN 1
VM
VM
VCP
CPH
AVDD
DVDD
VCC ⁽¹⁾
RREF
PIN 2
GND
GND
VM
CPL
GND
GND
nFAULT
GND
RECOMMENDED
Two X5R or X7R, 0.01-µF, VM-rated ceramic capacitors
Bulk, VM-rated capacitor
X5R or X7R, 0.22-µF, 16-V ceramic capacitor
X5R or X7R, 0.022-µF, VM-rated ceramic capacitor
X5R or X7R, 0.47-µF, 6.3-V ceramic capacitor
X5R or X7R, 0.47-µF, 6.3-V ceramic capacitor
>4.7-kΩ resistor
Resistor to limit chopping current must be installed. See the Typical Application
section for value selection.
(1) VCC is not a pin on the DRV8886AT device, but a VCC supply voltage pullup is required for open-drain output nFAULT; nFAULT may
be pulled up to DVDD
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 DRV8886AT device, the peak current rating is 3 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 actual operating rms current may be higher or lower depending on
heatsinking and ambient temperature. For the DRV8886AT device, 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. Because the
sinusoid amplitude is related to the rms current, the full-scale current is also determined by the thermal
considerations of the device. The full-scale current rating is approximately √2 × I_RMS. The full-scale current is set
by the RREF pin and the torque DAC when configuring the DRV8886AT device, for details see the Current
Regulation section. For the DRV8886AT device, the full-scale current rating is 2 A per bridge.
Full-scale current
RMS current
AOUT
BOUT
Step Input
Figure 12. Full-Scale and rms Current
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