DRV8426PWPR datasheet(9/49 Pages) TI1

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DRV8426

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SLOSE55 – MAY 2020

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7 Detailed Description

7.1 Overview

The DRV8426 device is an integrated motor-driver solution for bipolar stepper motors. The device provides the

maximum integration by integrating two N-channel power MOSFET H-bridges, current sense resistors and

regulation circuitry, and a microstepping indexer. The DRV8426 is pin-to-pin compatible with the DRV8424 and

DRV8425, with wide supply voltage of 4.5 to 33 V capable. DRV8426 provides an output current up to 2.5-A

peak, 1.5-A full-scale, or 1.1-A root mean square (rms). The actual full-scale and rms current depends on the

ambient temperature, supply voltage, and PCB thermal capability.

The DRV8426 device uses an integrated current-sense architecture which eliminates the need for two external

power sense resistors, hence saving significant board space, BOM cost, design efforts and reduces significant

power consumption. 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 by the voltage at the VREF pin.

A simple STEP/DIR interface allows for an external controller to manage the direction and step rate of the

stepper motor. The internal microstepping indexer can execute high-accuracy micro-stepping 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, 1/32, 1/64, 1/128, and 1/256 microstepping. High microstepping contributes to significant audible noise

reduction and smooth motion. In addition to a standard half stepping mode, a noncircular half stepping mode is

available for increased torque output at higher motor RPM.

Stepper motor drivers need to re-circulate the winding current by implementing several types of decay modes,

like slow decay, mixed decay and fast decay. The DRV8426 comes with smart tune decay modes. The smart

tune is an innovative decay mechanism that automatically adjusts for optimal current regulation performance

agnostic of voltage, motor speed, variation and aging effects. Smart tune Ripple Control uses a variable off-time,

ripple current control scheme to minimize distortion of the motor winding current. Smart tune Dynamic Decay

uses a fixed off-time, dynamic fast decay percentage scheme to minimize distortion of the motor winding current

while minimizing frequency content and significantly reducing design efforts. Along with this seamless, effortless

automatic smart tune, DRV8426 also provides the traditional decay modes like slow-mixed and mixed decay as

well.

A low-power sleep mode is included which allows the system to save power when not actively driving the motor.

DRV8426PWPR Datasheet(PDF) 9 Page - Texas Instruments