L6238 datasheet(26/35 Pages) STMICROELECTRONICS

Part #	L6238

Description	SENSORLESS SPINDLE MOTOR CONTROLLER

PDF	35 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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26 / 35 page

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

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

Figure 27: Bemf Amplifier.

Figure 28: Bemf Emulator.

L6238

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L6238 Datasheet(PDF) 26 Page - STMicroelectronics