ST72141K2 datasheet(41/132 Pages) STMICROELECTRONICS

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ST72141K

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MOTOR CONTROLLER (Cont’d)

The MTC manages these three events always in

the same order: Z generates C after a delay com-

puted in realtime, then waits for D in order to ena-

ble the peripheral to detect another Z event.

The speed regulation is managed by the micro-

controller, by means of an adjustable reference

current level in case of current control, or by direct

PWM duty-cycle adjustment in case of voltage

control.

All detections of Zn events are done during a short

measurement window while the high side switch is

turned off. For this reason the PWM signal is ap-

plied on the high side switches.

When the high side switch is off, the high side

winding is tied to 0V by the free-wheeling diode,

the low side winding voltage is also held at 0V by

the low side ON switch and the complete BEMF

voltage is present on the third winding: detection is

then possible.

Figure 26. Chronogram of Events (in Autoswitched Mode)

C event

Z event

Cn processing

Wait for Cn

Z > Zn min

C > Cn min

Wait for Dn

DH event

DS event

Wait for Z

VDD

VSS

P signal when sampled

(Output of the

VREF

(Threshold value for

Voltage on phase A

Voltage on phase B

Voltage on phase C

analog MUX)

Input comparator)

BEMF

sampling

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