TDA5341 Datasheet, PDF (12/28 Pages) NXP Semiconductors – Brushless DC motor and VCM drive circuit with speed control

Philips Semiconductors
Brushless DC motor and VCM drive circuit
with speed control
Product specification
TDA5341
Other design aspects
There are other design aspects concerning the application
of the TDA5341 besides the commutation function.
They are as follows:
• Generation of the tacho signal FG
• Motor control
• Current limiting
• Thermal protection.
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 µA 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 × 6 × 6 = 900 Hz and generates a tacho
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.
handbook, halfpage
100
Io
(% of Imax)
80
60
40
20
MGE822
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:
I_ILIM = 10020 × ^{2----.R--5---4--}
Where R = R (min.) = 19.5 kΩ and I_ILIM = 1.3 A.
If R < 19.5 kΩ, then I_ILIM is internally limited for device
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:
• 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).
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_DD goes below a
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).
0
0
1
2
3
4
5
control voltage (V)
Fig.5 Output current control.
1997 Jul 10
12