tdf5242t NXP Semiconductors, tdf5242t Datasheet - Page 8

• Manufacturer Part Number: tdf5242t
• Description: Brushless Dc Motor Drive Circuit
• Manufacturer: NXP Semiconductors

Philips Semiconductors
The convention for the inputs (inverting or not) is the same
as for a normal operational amplifier: with a resistor (as a
load) connected from the output (AMP OUT) to the positive
supply, a positive-going voltage is found when the
non-inverting input (+AMP IN) is positive with respect to
the inverting input ( AMP IN). Note that a ‘plus’ input
causes less current, and consequently a positive voltage.
M
DC motors can also be operated with analog control 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).
FG
The FG (Frequency Generator) signal is generated in the
TDF5242T by using the zero-crossing of the motor EMF
from the three motor windings and the commutation signal.
Output FG switches from HIGH-to-LOW on all zero
crossings and from LOW-to-HIGH on all commutations.
Output FG can source typically 75 A and sink more
than 3 mA.
Example: a 3-phase motor with 6 magnetic pole-pairs at
1500 rpm and with a full-wave drive has a commutation
frequency of 25
signal of 900 Hz.
1997 Sep 12
OTOR
Brushless DC motor drive circuit
SIGNAL
C
ONTROL
6
6 = 900 Hz, and generates a tacho
8
D
B
R
The output stages are protected in two ways:
RAKE FUNCTION
IRECTION FUNCTION
ELIABILITY
If the voltage on pin 7 is <2.3 V the motor is running in
one direction (depending on the motor connections)
If pin 7 is floating or the voltage is >2.7 V the motor is
running in the other direction.
If the voltage on pin 9 (pin BRAKE) is <2.3 V the motor
brakes; in this condition the external outputs are driven
to a HIGH voltage level
If pin 9 is floating or the voltage is >2.7 V the motor
runs normally.
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 in such a way that the transistors are switched
off when the junction temperature becomes too high.
Preliminary specification
TDF5242T