TDA5145TS datasheet(9/20 Pages) PHILIPS

9 / 20 page

1998 Oct 27

Philips Semiconductors

Product speciﬁcation

Brushless DC motor drive circuit

TDA5145TS

APPLICATION INFORMATION

(1) Value selected for 3 Hz start-up oscillator frequency.

Fig.6 Application diagram.

handbook, full pagewidth

MGR393

220

GND1

(1)

18 nF

µF

VMOT

123456789

BRAKE DIR

TDA5145TS

Introduction (see Fig.7)

Full-wave driving of a three phase motor requires three

push-pull output stages. In each of the six possible states

two outputs are active, one sourcing (H) and one sinking

(L). The third output presents a high impedance (Z) to the

motor, which enables measurement of the motor back

EMF in the corresponding motor coil by the EMF

comparator at each output. The commutation logic is

responsible for control of the output transistors and

selection of the correct EMF comparator. The sequence of

the six possible states of the outputs is given in Table 1.

The zero-crossing in the motor EMF (detected by the

comparator selected by the commutation logic) is used to

calculate the correct moment for the next commutation,

that is, the change to the next output state. The delay is

calculated (depending on the motor loading) by the

adaptive commutation delay block.

Because of high inductive loading the output stages

contain flyback diodes. The output stages are also

protected by a current limiting circuit and by thermal

protection of the six output transistors.

Table 1 Output states; note 1

Note

1. H = HIGH state; L = LOW state; Z = high-impedance

OFF-state.

The system will only function when the EMF voltage from

the motor is present. Therefore, a start oscillator is

provided that will generate commutation pulses when no

zero-crossings in the motor voltage are available.

A timing function is incorporated into the device for internal

timing and for timing of the reverse rotation detection.

STATE

MOT1

MOT2

MOT3

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