MC68HC705MC4MP datasheet(117/180 Pages) FREESCALE

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Pulse Width Modulator

Application Examples

General Release Specification

Pulse Width Modulator

10.9.2 Brushless DC Motor Interface

A typical interface for a three-phase brushless DC motor is shown in

Figure 10-18, although many other configurations are possible. The

rotor sensor usually consists of a Hall effect sensor, optical encoder, or

back-EMF detector. The coil current feedback is shown to be linear in

this example, using the on-chip A/D to provide torque data to the MCU.

Other systems may only require a current limit, which could be achieved

with an interrupt pin (which will offer some hysteresis) and an external

amplifier. With some reorganization of the I/O, it is also possible to

configure the device to drive two brushless motors simultaneously.

However, this will double the load on the processor. Depending upon the

complexity of the control algorithms adopted, and considering that the

commutation must be performed with software, care must be taken to

maintain commutation delays to within acceptable limits. The

commutation would follow the sequence shown in Table 10-5.

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MC68HC705MC4MP Datasheet(PDF) 117 Page - Freescale Semiconductor, Inc