12

Cur rent Contr ol

Digital Cur r ent Contr ol

The schematic example shown in Figure 3.7 illustrates

how the user might set up the 0 to 2V D/A reference to

control the output current of the driver.

Automatic Cur r ent Reduction

The IM2000S contains an auto-current reduction circuit

which will automatically set the CURRED output

HIGH approximately 1.5 seconds after the rising edge

of the last step clock pulse. This output, coupled with a

minimum of external components may be used to

reduce the current in the windings when the motor is at

a standstill.

The CURRED output will then be reset on the next rising edge of the step clock

input. This feature can greatly reduce motor and driver heating. It may also

increase power efficiency in systems not requiring full holding torque.

Note that although both phases are reduced by the same percentage when using

the Automatic Current reduction feature, motor shaft movement may occur,

depending on shaft positioning and load type.

Example Application of the Power Contr ol Outputs

Figure 3.6: Power Control Output Interface Examples

SIGNA

ENAN

PWMA

DIR

BRAKE

PWM

TFLAG

GND

DIR

BRAKE

PWM

TFLAG

GND

SIGNB

ENBN

PWMB

+5V

OVTMP

10k

VS

OUT1

BOOT1

BOOT2

OUT2

VSEN

VS

OUT1

BOOT1

BOOT2

OUT2

VSEN

6

2

1

11

10

8

6

2

1

11

10

8

3

4

5

9

7

3

4

5

9

7

IM2000 Interface for the

National Semiconductor LMD18200 &

International Rectifier IR8200B

PHASE A

PHASE B

IM2000

ENA

HLA

HRA

ENA

IN1

IN2

ENB

IN3

IN4

VSS

GND

ENB

HLB

HRB

VS

OUT1

OUT2

OUT3

OUT4

VSENB

VSENA

IM2000 Interface for the

SGS Thomson L298

PHASE A

PHASE B

IM2000

6

5

7

11

10

12

4

2

3

13

14

15

1

9

8

TO CURRENT

ADJUST CIRCUIT

CURRENT ADJUST

RESISTOR

CURRENT REDUCTION

RESISTOR

INPUT FROM

CURRED

VN0300 OR

EQUIVALENT

Figure 3.8: Automatic Current Reduction

Figure 3.7: Digital Current Control Example

INPUT FROM COUT

INPUT FROM DIR

X9C102

>INC

U/D

CS

VH

VW

VL

0 TO 2V REFERENCE

FOR D/A CONVERTERS

LM234Z

+V

+5V