NJM3717D2 データシートの表示（PDF） - Japan Radio Corporation

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NJM3717D2

STEPPER MOTOR DRIVER

Japan Radio Corporation  

| V MA – VMB |

50 %

t on

t off

VE

td

V

CH

NJM3717

t

fs =

1

ton + toff

Figure 3. Definition of terms

t

D=

ton

ton + toff

s FUNCTIONAL DESCRIPTION

The NJM3717 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 to M and low input from terminal M to M . A Schmitt trigger provides noise immunity and

A

B

B

A

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 I0 and I1 inputs determines the current level in the motor winding. Three fixed

current levels can be selected according to the table below.

Motor current

High level

I0

I1

100% L L

Medium level

60% H L

Low level

20% L H

Zero current

0% H H

The specific values of the different current levels are determined by the reference voltage VR together with the value

of the sensing resistor RS.

The peak motor current can be calculated as follows:

im = (VR • 0.083) / RS [A], at 100% level

im = (VR • 0.050) / RS [A], at 60% level

im = (VR • 0.016) / RS [A], at 20% level

The motor current can also be continuously varied by modulating the voltage reference input.

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