TDA5146T Datasheet, PDF (10/18 Pages) NXP Semiconductors – Brushless DC motor drive circuit

Philips Semiconductors
Brushless DC motor drive circuit
Product specification
TDA5146T
1. Value selected for 3 HZ start–up oscillator frequency
Figure 6. Application diagram without use of the FET driver stage
APPLICATION INFORMATION
Introduction
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 and one sinking current. The third output presents a high impedance to the motor which enables measurement of the motor 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 zero–crossing in the motor EMF (detected by the comparator selected by the commutation logic) is used to calculate the correct moment
for the neat 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.
The zero–crossings can be used to provide speed information such as the tacho signal FG.
1994 May 18
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