L8150 datasheet(24/37 Pages) STMICROELECTRONICS

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Precharge and hall effects filtering time description

L8150

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Precharge and hall effects filtering time description

6.1

Startup sequence with FS signal

●

Let’s startup sequence forced by FS comparator, assuming the motor is not rotating:

Figure 14.

Startup sequence forced by FS comparator, assuming the motor is not

rotating

When the signal coming from the FS comparator has a falling edge (corresponding to a Vsp

signal crossing the 1.23V threshold), the logic starts counting, to verify if the motor is

rotating or not. If the motor is stopped and no Hall effect commutation is detected, the

counter has reached its saturation time, given by the following equation:

N.B. TelMAX is equal to TMAX used in the previous sections of this document.

After this saturation time the logic has decided to do a precharge function, and for a period

of time given by the following equation all the output logic signals UL,VL,WL become high

while the signals UH, VH, WH are low.

When the precharge is over, the logic outputs start applying the right rectangular pattern to

accelerate the motor.

During this sequence the Hall filtering time is 400usec until the first rising edge on signal

HallU is detected. Then a filter given by the following equation is used:

∆ZC is the elapsed time between two consecutive zero-crossing signals. By default a zero-

crossing signal is generated when a falling edge of the FS comparator is detected, and after

that a zero-crossing signal is generated when a rising edge on signal HallU is detected.

PRECHARGE

HALL BUS

FILTER TIME

PHASES

PHASES EXCITED

400 us

T∆zc/576

T∆zc

Tel

TelMax/6

MOTOR ACCELERATING

400 us

Tel

MAX

7MHz

()

–

141.5msec

Tel

MAX

---------------------

24msec

≅

⇒

≅

CHARGE

4096 T

400

µsec

≅

⋅

FILTER

576

---------- T

∆

⋅

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