xOUT1

xOUT 2

VM

xISEN

xPHASE

Pre-

drive

VCP, VM

VM

PWM

OCP

OCP

xON

xVREF

Optional

Step

Motor

DAC

xI[4:0]

4

+

-

/5

DRV8834

SLVSB19A – FEBRUARY 2012 – REVISED MARCH 2012

www.ti.com

FUNCTIONAL DESCRIPTION

Device Configuration

The DRV8834 supports two configurations: phase/enable mode, where the outputs are controlled by phase

(direction) and enable signals for each H-bridge, and indexer mode, which allow control of a stepper motor using

simple step and direction inputs.

DC motors can only be controlled in phase/enable mode; indexer mode is not applicable to DC motors.

Stepper motors can be controlled using either phase/enable lode, or indexer mode.

The device is configured to be controlled either way using CONFIG pin. Logic HIGH on the CONFIG pin puts the

device in the STEP/DIR mode; logic LOW lets the motor to be controlled using the xPHASE/xENBL pins.

The state of the CONFIG pin is latched at power-up, and also whenever exiting sleep mode. CONFIG has an

internal pull-down resistor.

PWM Motor Drivers

DRV8834 contains two identical H-bridge motor drivers with current-control PWM circuitry. A block diagram of the

circuitry is shown below:

Figure 1. Motor Control Circuitry

Current Control

The current through the motor windings may be regulated by a fixed-frequency PWM current regulation, or

current chopping.

With stepping motors, current control is normally used at all times. Often it is used to vary the current in the two

windings in a sinusoidal fashion to provide smooth motion. This is referred to as microstepping. The DRV8834

can provide up to 1/32 step microstepping, using internal 5-bit DACs. Finer microstepping can be implemented

using the xPHASE/xENBL signals to control the stepper motor, and varying the xVREF voltages. The current

flowing through the corresponding H-bridge varies according to the equation given below. A very high degree of

microstepping can be achieved through this technique.

With DC motors, current control can be used to limit the start-up current of the motor to less than the stall current

of the motor.

8

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