Control signals

AN235

20/23

Doc ID 1679 Rev 2

the driver IC, as shown in Figure 17. Here a dedicated current control IC, the L6506,

combines the commutation signals with the current control signals and then passed the 6

lines to the driver IC. Some driver ICs, like the L6219 or the L6207, have the current control

built into the driver IC.

Figure 17.

Bipolar stepper motor drive implemented with the L6506 and the L6203

Alternatively, logic circuitry or a dedicated IC like the L297 can generate the control signals

from a step clock and direction signal. Figure 17 shows a drive circuit using the L297 and

the L6203. In this circuit the microcontroller needs to supply only the STEP and the

CW/CCW signals. Since most applications do not switch between full-step and half-step, the

HALF/FULL signal can usually be hard wired to the desired operation condition.

Figure 18.

Bipolar stepper motor driver implemented with the L297 and the L6203

As discussed earlier the torque ripple in half-step can be decreased by increasing the

current in the winding during the half-step states. The circuit in Figure 19 detects when one

off the inhibit lines is low and increased the voltage at the REF input of the L297 to increase

the current during the half-step.

AM16518v1

AM16515v1