L8150 datasheet(20/37 Pages) STMICROELECTRONICS

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Operating description

L8150

20/37

Figure 10.

Rectangular Drive Pattern (Reverse)

Smooth Drive mode is activated when three consecutive periods shorter than TMAX are

detected and device will keep driving in Smooth mode until an external command is applied

(through FR pin) or motor electrical period becomes longer than the maximum period the

device is able to follow.

Startup phase (rectangular driving) is activated in one of the following conditions:

●

when the Period Counter saturates;

●

when the desired rotation direction (coming from FR command) is different from the

detected rotation direction;

●

SD = High

→ Low

During all working conditions a current limitation circuit is active. It is composed of a

current comparator sensing current flowing in the sense resistor (usually a sense resistor is

connected between the sources of all power low side driver transistors and ground) and of

some control logic.

Current limitation is achieved in three possible ways according to the different motor

situations.

The current limiter control method is a consequence of the rotation speed and the detected

direction of the motor.

Let's divide the possible situations in two different cases:

The motor is rotating and its frequency is lower than the one used to switch between

rectangular and sinusoidal driving pattern

The motor is rotating and its frequency is bigger than the one used to switch between

rectangular and sinusoidal driving pattern

In case 1) even if the detected rotation direction is different from the desired direction, the

current limiter control method is to force two phases to GND and one phase is left in high

impedance state.

In case 2) the possible situations can be the following:

2a) The desired direction is equal to the detected direction and sinusoidal mode is applied,

the current limiter control method is forcing all the phases to GND

HallU

HallV

HallW

OutU

OutV

OutW

HallU

HallV

HallW

HallU

HallV

HallW

OutU

OutV

OutW

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