L8150 datasheet(17/37 Pages) STMICROELECTRONICS

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L8150

Operating description

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Figure 5.

16 bit counter operation

Smooth Drive basic functionality is to apply to the motor the voltage waveforms represented

in the following pictures (Figure 6) in case of forward rotation (CW).

Figure 6.

Smooth drive pattern (forward)

This kind of profile, which realizes waveforms that are differentially sinusoids, is digitally

described by a table of 36 8-bit samples stored in a decoding circuit. The final amplitude of

the voltage applied on the outputs is obtained by multiplying each sample by a value

generated through an 8-bit ADC, whose input is coming from the speed control.

The motor is controlled in voltage mode, so no current control compensation network is

required. Actuation is done on motor windings through a fixed frequency PWM conversion.

Since Smooth Drive is basically a voltage mode driving there can be the need of shifting the

applied profile with respect to the BEMF (here sensed through the Hall sensors). This

applied phase shift is called Torque Optimizer.

The value (expressed in electrical degrees, hereafter referred to as degrees) can be chosen

applying an analog voltage to TO pin, that will be internally converted using a 4-bit A/D.

The phase shift range is from 2.5 to 40 degrees with a 2.5-degrees step. As a reference the

correspondence between phase shift values and analog voltages is reported in Table 21.

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