AN2785 datasheet(21/51 Pages) STMICROELECTRONICS

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AN2785

Application examples

Doc ID 14785 Rev 1

21/51

Figure 14.

Waveform related to the VM application circuit with linear hall sensor

6.3

Full-bridge topology: brush DC motor driver

This section provides a further sample circuit using L6393 ICs to drive a typical brush DC

motor. Again, the power stage topology used is full-bridge. Considering that the voltage

mode control circuit is a simplification of the one implementing current mode control, only

this last example is shown in the application circuit depicted in Figure 15.

The direction of the brush DC motor is selected by the DIRECTION signal, which is directly

connected to the PHASE input of one driver and, once inverted, to the PHASE input of the

other L6393 driver. The inversion of the PHASE signal is implemented using one L6393

comparator. The torque applied to the DC motor is controlled by the Vth signal which works

as reference signal for a peak current control implemented using the other available L6393

comparator. The type of control is a peak current control with constant OFF time. It is

possible to control the torque and thus indirectly also the speed of the motor, assuming that

the load torque and the bus voltage remain constant.

The suggested circuit makes it possible to implement a simple brush DC motor driver using

just two L6393s, a few simple passive components and a power full-bridge.

Sinewave

HALL signals

Current

protection

Output

current

PWM generation

with minimum

speed

RD signal

AN2785 Datasheet(PDF) 21 Page - STMicroelectronics