DRV8886AT Datasheet, PDF (11/40 Pages) Texas Instruments – 2-A Stepper Motor Driver With Integrated Current Sense and AutoTune Technology

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7 Detailed Description
DRV8886AT
SLVSDO1 – JANUARY 2017
7.1 Overview
The DRV8886AT device is an integrated motor-driver solution for bipolar stepper motors. The device integrates
two N-channel power MOSFET H-bridges, integrated current sense and regulation circuitry, and a microstepping
indexer. The DRV8886AT device can be powered with a supply voltage from 8 to 37 V and is capable of
providing an output current up to 3-A peak, 2-A full-scale, or 1.4-A root mean square (rms). The actual full-scale
and rms current depends on the ambient temperature, supply voltage, and PCB thermal capability.
The DRV8886AT device uses an integrated current-sense architecture which eliminates the need for two external
power sense resistors. This architecture removes the power dissipated in the sense resistors by using a current
mirror approach and using the internal power MOSFETs for current sensing. The current regulation set point is
adjusted with a standard low-power resistor connected to the RREF pin. This features reduces external
component cost, board PCB size, and system power consumption.
A simple STEP/DIR interface allows for an external controller to manage the direction and step rate of the
stepper motor. The internal indexer can execute high-accuracy microstepping without requiring the external
controller to manage the winding current level. The indexer is capable of full step, half step, and 1/4, 1/8, 1/16
microstepping. In addition to a standard half stepping mode, a noncircular half stepping mode is available for
increased torque output at higher motor RPM.
The current regulation is configurable between several decay modes. The decay mode can be selected as a
slow-mixed, mixed decay, AutoTune Ripple Control, or AutoTune Dynamic Decay current regulation scheme.
The slow-mixed decay mode uses slow decay on increasing steps and mixed decay on decreasing steps. The
AutoTune decay modes automatically adjust for optimal current regulation performance and compensate for
motor variation and aging effects. AutoTune Ripple Control uses a variable off-time, ripple control scheme to
minimize distortion of the motor winding current. AutoTune Dynamic Decay uses a fixed off-time, dynamic decay
percentage scheme to minimize distortion of the motor winding current while also minimizing frequency content.
An adaptive blanking time feature automatically scales the minimum drive time with output current level. This
feature helps alleviate zero-crossing distortion by limiting the drive time at low-current steps.
A torque DAC feature allows the controller to scale the output current without needing to scale the RREF
reference resistor. The torque DAC is accessed using a digital input pin which allows the controller to save
system power by decreasing the motor current consumption when high output torque is not required.
A low-power sleep mode is included which allows the system to save power when not actively driving the motor.
Copyright © 2017, Texas Instruments Incorporated
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