AN1495

L6506 and L6203/L298

Doc ID 8700 Rev 3

17/25

6

L6506 and L6203/L298

Microstepping drives can be implemented using the L6506 controller and bridge IC's like the

L6201, L6202, L6203 and L298. The main difference between the standard half step

application and a microstepping application is that the two references of the L6506 are set

by D/A converter outputs. Figure 15 and Figure 16 show microstepping applications using

the L6506 and the L6203. Outputs Px1 through Px4 from the microprocessor set the phase

for the L6506/L6203 combination and output Px5 and PX6 are used to enable the bridges.

Again, the D/A function could be implemented using the PWM outputs of the

microprocessor as was done in the example above or it could be implemented using and

integrated D/A. The same logic configuration can be used with the L6201, L6202 or L298.

When using the typical connection between the L6506 and the L6203 (as shown in

Figure 15), the PWM signal is applied to one of the phase inputs (the phase that is normally

high) and you get the slow decay mode of operation.

To implement the fast decay mode of operation, the PWM signal needs to be applied to the

ENABLE inputs of the L6203s. This can be accomplished by rearranging the connections

from the microprocessor. Inputs IN 1 and IN 2 of the L6203s are disconnected from the

L6506 and connected directly to the Px1 through Px4 outputs of the microprocessor, which

will continue to provide the phase information as before. The two PWM current control loops

in the L6506 are then used to control the ENABLE inputs of the two L6203, as shown in

Figure 16. Px5 and Px6 are now connected to the inputs of the L6506 so that each bridge

can be disabled to get zero current. Finally the power on reset (POR) is connected to the

RESET input of the L6506 to disable the bridge during power up.

Figure 15.

Microstepping using L6506 and L6203 (slow decay)

IN 1

IN 4

IN 3

IN 2

IN 1

IN 2

Enable

Vref

IN 1

IN 2

Enable

Vref

OUT 1

OUT 4

OUT 3

OUT 2

OUT 1

OUT 2

BOOT 2

BOOT 1

GND

SENSE

OUT 1

OUT 2

BOOT 2

BOOT 1

GND

SENSE

L6506

L6203

L6203

OSC

Q

R

S

Q

R

S

SENSE

RESISTORS

220 nF

MOTOR

WINDING

MOTOR

WINDING

220 nF

Vref B

Vref A

From D/A

RESET

Microprocessor

Microprocessor

POR

AM15156v1