MTD6505 MICROCHIP [Microchip Technology], MTD6505 Datasheet - Page 9

• Manufacturer Part Number: MTD6505
• Description: Sinusoidal Sensorless 3-Phase Brushless DC Fan Motor Driver
• Manufacturer: MICROCHIP [Microchip Technology]

4.0
The MTD6505 generates a full-wave signal to drive a
3-phase BLDC motor. High efficiency and low-power
consumption are achieved due to CMOS transistors
and synchronous rectification drive type.
4.1
The rotational speed of the motor can be controlled
either through the PWM digital input signal or by acting
directly on the power supply (V
signal is High (or left open), the motor rotates at full
speed. When the PWM signal is low, the IC outputs are
set to high-impedance and the motor is stopped.
By changing the PWM duty cycle, the speed can be
adjusted. Thus, the user has maximum freedom to
choose the PWM system frequency within a wide range
(from 1 kHz to 100 kHz).
Since the PWM pin has an internal pull-up resistor
connected to V
between 0V and High-Z. The PWM driver must be able
to support the pull-up resistor current, in order to drive
the pin. See “PWM Internal Pull-Up Resistor” in
Section 1.0, Electrical
The output transistor activation always occurs at a fixed
rate of 30 kHz, which is outside of the range of audible
frequencies.
4.2
The current-carrying order of the outputs depends on
the DIR pin state (“Rotation Direction”) and is described
in
direction change during operation.
TABLE 4-1:
 2011 Microchip Technology Inc.
Connected
to GND
or Floating
Connected
to V
DIR Pin State
Note 1: The PWM frequency has no direct affect
Note 2: The standard output frequency is 30 kHz.
Table
BIAS
4-1. The DIR pin is not designed for dynamic
FUNCTIONAL DESCRIPTION
Speed Control
Motor Rotation Direction
on the motor speed and is asynchronous
with
transistors.
A 20 kHz output frequency option is
available upon request.
DD
Direction
Rotation
MOTOR ROTATION
DIRECTION OPTIONS
(DIR PIN)
Forward
Reverse
the
, it is recommended to drive it
Characteristics.
activation
OUT1  OUT2  OUT3
OUT3  OUT2  OUT1
Outputs Activation
DD
). When the PWM
Sequence
of
the
output
4.3
The Frequency Generator output (FG) is a “Hall-effect
sensor equivalent” digital output, giving information to
an external controller about the speed and phase of the
motor. The FG pin is an open drain output, connecting
to a logical voltage level through an external pull-up
resistor. When a lock, or an out-of-sync situation is
detected by the driver, this output is set to high-
impedance until the motor is restarted. Leave the pin
open when it is not used.
4.4
If the motor is blocked and cannot rotate freely, a lock-
up protection circuit detects it and disables the driver by
setting its outputs to high-impedance to prevent the
motor coil from burnout. After a “waiting time” (T
the lock-up protection is released and normal operation
resumes for a given time (T
blocked, a new period of waiting time is started. T
and T
nal capacitor is required.
4.5
The motor peak current is limited by the driver to
750 mA (standard value), thus limiting the maximum
power dissipation in the coils.
4.6
The MTD6505 device has a thermal protection function
which detects when the die temperature exceeds
T
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. When the junction temperature
(T
The thermal detection circuit has +25°C hysteresis.
FIGURE 4-1:
Hysteresis.
J
J
= +170°C. When this temperature is reached, the
) drops below +145°C, normal operation resumes.
RUN
operation
Normal
Frequency Generator Function
Lockup Protection and Automatic
Restart
Overcurrent Protection
Thermal Shutdown
timings are fixed internally, so that no exter-
+145°
Thermal Protection
+170°
RUN
Thermal shutdown
MTD6505
). If the motor is still
DS22281A-page 9
T
J
WAIT
WAIT
),