NJM37717 New Japan Radio Co., Ltd., NJM37717 Datasheet - Page 3

• Manufacturer Part Number: NJM37717
• Description: STEPPER MOTOR DRIVER
• Manufacturer: New Japan Radio Co., Ltd.

The NJM37717 is intended to drive a bipolar constant current through one motor winding of a 2-phase stepper
motor.
Current control is achieved through switched-mode regulation, see figure 4 and 5.
Three different current levels and zero current can be selected by the input logic.
The circuit contains the following functional blocks:
• Input logic
• Current sense
• Single-pulse generator
• Output stage
Input logic
Phase input. The phase input determines the direction of the current in the motor winding. High input forces the
current from terminal M
a delay circuit eliminates the risk of cross conduction in the output stage during a phase shift.
Half- and full-step operation is possible.
Current level selection. The status of I
current levels can be selected according to the table below.
Motor current
High level
Medium level
Low level
Zero current
The specific values of the different current levels are determined by the reference voltage V
of the sensing resistor R
The peak motor current can be calculated as follows:
i
i
i
The motor current can also be continuously varied by modulating the voltage reference input.
m
m
m
= (V
= (V
= (V
FUNCTIONAL DESCRIPTION
R
R
R
• 0.083) / R
• 0.050) / R
• 0.016) / R
Figure 3. Definition of terms
100% L
60% H
20% L
0%
S
S
S
[A], at 100% level
[A], at 60% level
[A], at 20% level
A
S
to M
.
I
H
0
B
and low input from terminal M
I
L
L
H
H
1
0
and I
1
inputs determines the current level in the motor winding. Three fixed
B
to M
A
. A Schmitt trigger provides noise immunity and
R
together with the value
NJM37717