tda5240t NXP Semiconductors, tda5240t Datasheet - Page 15

• Manufacturer Part Number: tda5240t
• Description: Brushless Dc Motor Drive Circuit
• Manufacturer: NXP Semiconductors

There are other design aspects concerning
The FG signal is generated
Philips Semiconductors
OTHER DESIGN ASPECTS
.Generation
.Built-in
.Reliability
FG SIGNAL
therefore
negative-going
The accuracy
electromagnetic
Two FG frequencies
frequency
The accuracy of the PG signal in applications
that a ahort LOW-time
Every zero-crossing
resistor must be connected
Example: A three phase motor with 6 magnetic
PG SIGNAL
by combining
signal (PGIN) is only used as an indicator to select a particular
RELIABILITY
It is necessary to protect high current circuits and the output stages are protected in two ways:
November
Brushless
interface for a PG sensor.
half the commutation
of 25 x 6 x 6 = 900 Hz, and generates
96
.
the accurate
of the tacho signal FG
of the FG output signal Oitter) is very good. This accuracy
edges are called FG pulses because they generate an interrupt in a controlling
construction,
PG IN
MOT3
PG/FG~~~~
DC motor drive circuit
in a (star connected)
are given out: 6 times the number of poles pairs or 3 times the number of poles pairs. A pull-up
of 15 ~s after a HIGH to LOW transition.
FG signal with the PG signal by using a wide tolerance
in the TDA5240T
to PGFG outputs
which also effects the satisfactory
frequency.
vAv
Fig.9 Timing of the FG and PG signals
motor winding is used to toggle the FG output signal. The FG frequency
All transitions
the application
by using the zero-crossing
such as VCR must be high (phase information.
toleronce
pole-pairs
a tacho signal of 450 Hz.
on
indicate the detection
15/19
of the TDA5240T
at 1500 rpm and with a full-wave
PG
IN
FG pulse. This pulse differs from the other FG pulses in
All other FG pulses have a 50% duty factor (see Fig. 9).
functioning
vAv
of the motor EMF from the three motor windings.
depends on the symmetry
besides the commutation
of the motor itself.
of a zero-crossing
external PG sensor. The external PG
drive has a commutation
~
This accuracy
microprocessor.
(except for PG). The
Product specification
of the motor's
TDA5240T
function. They are:
is obtained
is