A OU T 1

A OU T2

BOU T1

B OU T2

Step

Motor

VM

VM

A IS EN

B ISEN

APH A SE

Pre-

drive

Pre-

drive

VC P, VGD

VM

VM

+

-

PW M

V CP, VGD

+

-

PW M

A BVR EF

OC P

OC P

OC P

OC P

A BD EC A Y

B EN BL

DAC

DAC

A = 5

A = 5

A I[2:0]

B I[2:0]

3

3

AEN B L

BPH A SE

A I[2:0]

3

From Indexer Logic

DRV8821

www.ti.com

SLVS912J – JANUARY 2009 – REVISED JANUARY 2016

Feature Description (continued)

Figure 10. Block Diagram

Note that there are multiple VM motor power supply pins. All VM pins must be connected together to the motor

supply voltage.

7.3.2 Current Regulation

The PWM chopping current is set by a comparator which compares the voltage across a current sense resistor

connected to the xISEN pins, multiplied by a factor of 5, with a reference voltage. The reference voltage is input

from the xVREF pin.

Copyright © 2009–2016, Texas Instruments Incorporated

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