Philips Semiconductors
Product specification
Brushless DC motor drive circuit
TDA5144
MOTOR CONTROL
DC motors can be controlled in an analog manner using
the OTA.
For the analog control an external transistor is required.
The OTA can supply the base current for this transistor
and act as a control amplifier (see Fig.8).
RELIABILITY
It is necessary to protect high current circuits and the
output stages are protected in two ways:
• Current limiting of the ‘lower’ output transistors. The
‘upper’ output transistors use the same base current as
the conducting ‘lower’ transistor (+15%). This means
that the current to and from the output stages is limited.
• Thermal protection of the six output transistors is
achieved by each transistor having a thermal sensor
that is active when the transistor is switched on. The
transistors are switched off when the local temperature
becomes too high.
It is possible, that when braking, the motor voltage (via the
flyback diodes and the impedance on VMOT) may cause
higher currents than allowed (>0.6 A). These currents
must be limited externally.
June 1994
15
NXP [ NXP ]
