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AN469

APPLICATION NOTE

November 2003

The L6506 is a linear integrated circuit designed to sense and control the current in stepping motors and other

similar devices. When used in conjunction with power stages like the L293, L298N, or L7180 the chip set forms

a constant current drive for inductive loads and performs all the interface functions from the control logic through

the power stage.

The L6506 may be used with either two phase bipolar or four phase unipolar motor configurations. The circuit

in figure 1 shows the L6506 used in conjunction with the L298N in a 2 phase bipolar stepper motor application.

The circuit in figure 2 implements a similar 4 phase unipolar application.

CURRENT CONTROL LOGIC

In these two circuits, the L6506 is used to sense and control the current in each of the load windings. The current

is sensed by monitoring the voltage across a sense resistor (Rsense) and using a Pulse Width Modulated con-

trol to maintain the current at the desired value.

An on-chip oscillator drives the dual chopper and sets the operating frequency. An RC network on pin 1 sets the

operating frequency, which is given by the equation :

(1)

for R1 > 10 K

Ω

Figure 1. Application Circuit for Bipolar 2 Phase Stepper Motor.

f

1

0.69R1 C1

----------------------------

=

by Thomas Hopkins

USING THE L6506 FOR CURRENT CONTROL

OF STEPPING MOTORS

Chopper-type current control circuits improve the performance of motor drives. This note shows how

this can be done simply using the L6506 current controller IC.