TDA5341 Philips Semiconductors, TDA5341 Datasheet - Page 12

• Manufacturer Part Number: TDA5341
• Description: Brushless DC motor and VCM drive circuit with speed control
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Other design aspects
There are other design aspects concerning the application
of the TDA5341 besides the commutation function.
They are as follows:
FG signal
The FG signal is generated in the TDA5341 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 LOW-to-HIGH on all commutations
and can source more than 40 A and sink more than
1.6 mA.
Example: A three-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.
Motor control
Figure 5 shows the spindle transconductance by giving the
relative output current as a function of the voltage applied
to pin CNTRL.
1997 Jul 10
handbook, halfpage
Generation of the tacho signal FG
Motor control
Current limiting
Thermal protection.
(% of I max )
Brushless DC motor and VCM drive circuit
with speed control
I o
100
80
60
40
20
0
0
Fig.5 Output current control.
6
1
6 = 900 Hz and generates a tacho
2
3
control voltage (V)
4
MGE822
5
12
Current limiting
Outputs MOT1 to MOT3 are protected against high
currents in two ways; current limiting of the ‘lower’ output
transistor and current limiting of the ‘upper’ one.
This means that the current from and to the output stages
is limited.
It is possible to adjust the limiting current externally by
using an external resistor connected between pin ILIM and
ground, the value is determined by the formula:
Where R = R (min.) = 19.5 k and I
If R < 19.5 k , then I
protection purposes.
Thermal protection
Thermal protection of the six output transistors of the
spindle section 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. In that event, a
RESET is automatically generated to the external world by
pulling RESETOUT LOW.
Reset section
This circuit provides the following:
The power-up reset signal (RESETOUT) applied to
external circuits as a digital output is typically 150 ms after
power-up. In the same way, as soon as V
threshold that is externally set (UVDIN2), RESETOUT
goes LOW. The under voltage detection threshold is
adjustable with external resistors (see Fig.8).
The reset circuitry has a minimum output pulse (100 ms)
even for brief power interruptions (higher than 1 ms).
The pulse duration can be adjusted with an external
capacitor (UVDIN1).
I
ILIM
An external signal that sends a RESETOUT (active
LOW) to the disk drive circuitry at power-up and
power-down
Causes actuator to retract (PARK).
=
10020
2.54
---------- -
R
ILIM
is internally limited for device
ILIM
Product specification
= 1.3 A.
TDA5341
DD
goes below a