L6238 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6238' PDF : 35 Pages View PDF
L6238
Figure 27: Bemf Amplifier.
For laboratory evaluation purposes, a simple re-
sistive network as shown in figure 28 can be used
to emulate the Bemf of the motor.
The actual Bemf zero-crossing is 30 electrical de-
grees (50% of a commutation interval) away from
the optimal switch point. A digital counter circuit
measures 50% of the previous interval to deter-
mine the next interval’s commutation delay from
the zero crossing. During the low RPM stages of
Figure 28: Bemf Emulator.
start up the long commutation intervals may
cause the counter to overflow, in which case 50%
of the max count will be less than 50% of the
ideal commutation interval. Therefore, the torque
will not be optimal until the desired commutation
interval is less than the dynamic range of the
counter.
6.0 SERIAL PORT
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