MTD6502B Ver la hoja de datos (PDF) - Microchip Technology
Número de pieza
componentes Descripción
Fabricante
MTD6502B Datasheet PDF : 20 Pages
| |||
3.0 FUNCTIONAL DESCRIPTION
The MTD6502B generates a full-wave signal to drive a
3-phase sensorless BLDC motor. High efficiency and
low-power consumption are achieved due to the CMOS
transistors and synchronous rectification drive type.
3.1 Speed Control
The rotational speed of the motor can be controlled
either through the PWM digital input signal, or by acting
directly on the power supply (VCC). When the PWM sig-
nal is High (or left open), the motor rotates at full speed.
When the PWM signal is Low, the motor is stopped
(and the IC outputs are set to high-impedance). By
changing the PWM duty cycle, the speed can be
adjusted. Notice that the PWM frequency has no spe-
cial meaning for the motor speed and is asynchronous
with the activation of the output transistors. Thus, the
user has the maximum freedom to choose the PWM
system frequency within a wide range (from 1 kHz to
100 kHz), while the output transistor activation always
occurs at a fixed rate (20 kHz, or 30 kHz), which is out-
side of the range of audible frequencies.
Note:
The standard output frequency is 30 kHz.
The 20 kHz output frequency option is
available upon request.
3.2 Motor Rotation Direction
The current carrying order of the outputs depends on
the DIR pin state (Rotation Direction) according to
Table 3-1.
TABLE 3-1:
MOTOR ROTATION
DIRECTION OPTIONS
(DIR PIN)
DIR Pin State
Rotation
Direction
Outputs Activation
Sequence
Connected to
GND or
Floating
Forward OUT1 OUT2 OUT3
Connected to
VDD
Reverse OUT3 OUT2 OUT1
3.3 Frequency Generator Function
The Frequency Generator output (FG) is a “Hall-sensor
equivalent” digital output, that gives information to an
external controller about the speed and phase of the
motor. The FG pin is an open collector output, connect-
ing to a logical voltage level through an external pull-up
resistor. When a lock (or out-of-sync) situation is
detected by the driver, this output is set to high-imped-
ance until the motor is restarted. Leave the pin open
when not used.
Note: FG/2 option is available upon request for
8-pole applications.
2011 Microchip Technology Inc.
MTD6502B
3.4 Lock-up Protection and Automatic
Restart
If the motor is blocked and cannot rotate freely, a
lock-up protection circuit detects this situation and dis-
ables the driver (by setting its outputs to high-imped-
ance), in order to prevent the motor coil from burnout.
After a “waiting time” (TWAIT), the lock-up protection is
released and normal operation resumes for a given
time (TRUN). If the motor is still blocked, a new period
of waiting time is started. TWAIT and TRUN timings are
fixed internally, so that no external capacitor is needed.
3.5 Overcurrent Protection
The motor peak current is limited by the driver to a fixed
value (defined internally), thus limiting the maximum
power dissipation in the coils.
3.6 Thermal Shutdown
The MTD6502B has a thermal protection function
which detects when the die temperature exceeds
TJ = +170°C. When this temperature is reached, the
circuit enters the Thermal Shutdown mode, and the
outputs OUT1, OUT2 and OUT3 are disabled (high-
impedance), avoiding the IC destruction and allowing
the circuit to cool down. Once the junction temperature
(TJ) has dropped below +145°C, the normal operation
resumes (thermal detection circuit has +25°C hystere-
sis function).
Thermal shutdown
Normal
operation
+145° +170°
TJ
FIGURE 3-1:
Hysteresis.
Thermal Protection
3.7 Internal Voltage Regulator
VDD voltage is generated internally and is used to sup-
ply the internal logical blocks. The VDD pin is used to
connect an external decoupling capacitor (1 µF, or
higher). Notice that this pin is for IC internal use, and is
not designed to supply DC current to external blocks.
DS25003A-page 9
Share Link: 