AN235

Control signals

Doc ID 1679 Rev 2

19/23

Figure 16.

Current waveforms during transition from full-step to half-step state

To get the fastest decay from a full-step to a half-step state the bridge should be disabled so

that both of the transistors that were on are switched off. This puts the bridge in a fast decay

mode and the current decays more quickly, as shown in Figure 16 c. For half-step operation

an additional two signals are required to inhibit the bridge and put it in tristate during the

steps when there is no current in that phase. Figure 15 shows the drive signals required for

a driver like the L298 or L6203.

The six commutation signals can easily be generated from a microcontroller, but the current

control is typically implemented in circuitry that is added between the microcontroller and

AM16514v1