OUT1

OUT2

DCM

VM

ISEN

IN2

Pre-

drive

VCP, VGD

VM

+

-

PWM

VREF

OCP

OCP

DECAY

DAC

A = 5

IN1

I[4:0]

5

DRV8842-EP

www.ti.com

SLVSCH4 – JULY 2014

8.3 Feature Description

8.3.1 PWM Motor Drivers

The DRV8842-EP contains one H-bridge motor driver with current-control PWM circuitry. Figure 4 shows a block

diagram of the motor control circuitry.

Figure 4. Motor Control Circuitry

Note that there are multiple VM, ISEN, OUT, and VREF pins. All like-named pins must be connected together on

the PCB.

8.3.2 Bridge Control

The IN1 and IN2 input pins directly control the state of the OUT1 and OUT2 outputs. Either input can also be

used for PWM control of the load. Table 1 shows the logic.

Table 1. H-Bridge Logic

IN1

IN2

OUT1

OUT2

0

0

L

L

0

1

L

H

1

0

H

L

1

1

H

H

The control inputs have internal pulldown resistors of approximately 100 k

Ω.

8.3.3 Current Regulation

The maximum current through the load is regulated by a fixed-frequency PWM current regulation, or current

chopping. When the H-bridge is enabled, current rises through the winding at a rate dependent on the DC

voltage and inductance of the winding. After the current hits the current chopping threshold, the bridge disables

the current until the beginning of the next PWM cycle.

For DC motors, current regulation is used to limit the start-up and stall current of the motor. Speed control is

typically performed by providing an external PWM signal to the IN1 or IN2 input pins.

If the current regulation feature is not needed, it can be disabled by connecting the ISEN pins directly to ground

and the VREF pins to V3P3.

Copyright © 2014, Texas Instruments Incorporated

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