35

SI-7115B

s Thermal design

In SI-7115B, the avalanche diode of the phase-switching

transistor is operated in breakdown condition and the en-

ergy built up in the inductance of the motor coil is dissipated

as heat of the transistor. Hence, when the motor rotates,

the internal heat dissipation increases compared with when

the motor is stopped.

Therefore, the internal heat dissipation of 7115B can be

computed from the data taken with actual load through the

following procedures.

(1) Vary the rotation speed of the motor within the actual

operating range in a circuit under actual load conditions

(2) Obtain the internal power dissipation Pdiss (4-phase) of

7115B through the following formula.

The figure below shows the relationship between frequency

SI-7115B

Torque characteristics

2-phase

excitation

1-2 phase excitation

50

100

500

1000

5000

Frequency (PPS)

Motor

103G–775–1240

0

1.0

2.0

φ

50

100

500

1000

5000

Frequency (PPS)

5.0

4.0

3.0

2.0

1.0

0

Motor KP6M2-001

SI-7115B

Torque characteristics

2-phase excitation

φ

8

13

10

15

1

2

4

5

3

17

6

7

9

14

16

11

12

A

B

A

B

Excitation

signals

F

2.2

10V

+

–

Rx

b

a

AA

B

B

A

A

A

Method for measuring current

(circuit under actual load conditions)

15

SI-7115B

Stepper motor

µ

SI-7115B Frequency vs. Supply current, Internal power

dissipation and Case temperature (Example)

Power down circuit

2

4

5

3

SI-7115B

1500

1000

500

0

Frequency (PPS)

0

0

0

50

10

1

100

20

2

adjacent to SI-7115B

A

A

A

SI

7115B

AB AB

M

Motor : 23 PM-C109 no load

= 1.0A/

2-phase excitation

Heatsink 100 x 100 x 2A

Ta = 25°C

max

φ

Application Note

s Power down mode

The SI-7115B can be operated in power down mode. The

circuit is shown below.

As shown in the figure,

when the power down tran-

sistor is switched on, (Ry

is power down resistor)

fixing resistance and the

current during power down

mode can be obtained by

substituting this resistance

A.

s Example of Frequency vs.

Torque characteristics

The following two graphs show the relationship between

frequency (pps) and pull-out torque (kg - cm) of SI-7115B

when used with two types of motor.