Data Sheet

xOUT1

xOUT2

xISEN

From Logic

Pre-

drive

VCP, VM

PWM

OCP

Optional

Step

Motor

DAC

Comparator

CONFIG

xVREF

From Indexer

DRV8834

SLVSB19D –FEBRUARY 2012–REVISED MARCH 2015

www.ti.com

Feature Description (continued)

Figure 6. Motor Control Circuitry

8.3.1 Current Control

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

Current regulation works as follows:

When an H-bridge is enabled, current rises through the winding at a rate dependent on the supply voltage and

inductance of the winding. If the current reaches the current chopping threshold, the bridge disables the current

until the beginning of the next PWM cycle. Immediately after the current is enabled, the voltage on the xISEN pin

is ignored for a period of time before enabling the current sense circuitry. This blanking time also sets the

minimum on time of the PWM when operating in current chopping mode.

Product Folder Links: DRV8834