TDA5145TS Datasheet, PDF (9/20 Pages) NXP Semiconductors – Brushless DC motor drive circuit

Philips Semiconductors
Brushless DC motor drive circuit
APPLICATION INFORMATION
Product specification
TDA5145TS
handbook, full pagewidth
GND1
(1)
18 nF
10 220
nF nF
24 23 22 21 20 19 18 17 16 15 14 13
TDA5145TS
1 2 3 4 5 6 7 8 9 10 11 12
BRAKE DIR
18 nF
VMOT
10 µF
VP
MGR393
(1) Value selected for 3 Hz start-up oscillator frequency.
Fig.6 Application diagram.
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
STATE
1
2
3
4
5
6
MOT1
Z
H
H
Z
L
L
MOT2
L
L
Z
H
H
Z
MOT3
H
Z
L
L
Z
H
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.
1998 Oct 27
9