NJM3772

s APPLICATIONS INFORMATION

Current control

The output current to the motor winding is determined by the voltage at the reference input and the sensing

resistor, R

Chopping frequency, winding inductance and supply voltage also affect the current, but to much less extent.

The peak current through the sensing resistor (and motor winding) can be expressed as:

I

i.e., with a recommended value of

0.47 ohm for the sensing resistor R

960 mA.

To improve noise immunity on the V

is correspondingly

changed to 1 ohm.

Figure 7. Microstepping system with NJU39610 and NJM3772

E

C

E

C

GND

RC

NJM3772

15 k

Ω

3300 pF

820 pF

0.5

Ω

1 k

Ω

1 k

Ω

0.5

Ω

820 pF

STEPPER

MOTOR

M

M

M

M

A1

B1

A2

B2

VV

V

V

V

CC

MM1

BB1

MM2

BB2

+5 V

12

8

4

7

19

20

26

25

22

18

11

27

5

23

1,

2,

3,

9,

28, 13,

14, 15,

16, 17,

10

24

6

21

Phase

V

Phase

V

R2

1

R1

2

D1

D3

0.5

Ω

11

2

2

D1 - D4 are UF 4001 or

BYV 27, t

100 ns

rr

R S

R S

0.5

Ω

R B

R B

0.1

µF

+

10

µF

D2

D4

Pin numbers refer to

PLCC package.

D0

D7

A0

A1

WR

CS

RESET

VV

NJU39610

6

10

4

12

2

14

9

27

15

7

28

1

16

25

To

mP

+2.5V

Sign

DA

1

1

Sign

DA

2

2

SS

Ref

V

(+5V)

CC

E

C

E

C

GND

RC

NJM3772

15 k

Ω

3300 pF

820 pF

0.5

Ω

1 k

Ω

1 k

Ω

0.5

Ω

820 pF

STEPPER

MOTOR

M

M

A1

B1

V

MM

VV

V

V

V

CC

MM1

BB1

MM2

BB2

+5 V

12

19

22

18

11

27

5

23

1,

2,

3,

9,

28, 13,

14, 15,

16, 17,

10

24

6

21

Phase

V

Phase

1

R1

2

D1

D3

0.5

Ω

1

1

22

0.5

Ω

R

B

R

B

GND (V

)

CC

+5 V

0.1

µ F

+

10

µF

D2

D4

D1 - D4 are UF 4001 or

BYV 27, t

≤ 100 ns.

rr

Pin numbers

refer to PLCC

package.

GND (V

)

MM

20

26

25

M

B2

8

4

7

Figure 6. Typical stepper motor driver application with NJM3772