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HT66FM5440
Brushless DC Motor A/D Flash MCU
HT66FM5440
Brushless DC Motor A/D Flash MCU
Application Circuits
Introduction
Holtek’s HT66FM5440 is specially directed at three-phase BLDC motor control applications. Acting
like a human brain, the device is the main power control core of the BLDC motor driving systems,
which takes the responsibility to immediately collect and transmit information. The BLDC motor
sensor driving solution relies on the Hall sensor to sense the magnetic field of the motor rotor and
then drives the corresponding motor phase based on the Hall sensor signal, sequentially achieving
phase change purpose. Therefore, it is necessary to first understand the relationship between the
Hall sensor signal and motor phase. However, there is no such problem for the sensorless driving
solution. Motor driving is divided into two types, square-wave control and sine-wave control, which
are both supported by the device. In a general driving system, system voltage and current detection
as well as speed command are necessary. Power component temperature and motor temperature
detection, etc., may also be needed in accordance with different products. Basing on the basic
functional requirements mentioned above, this chapter will introduce how to use the HT66FM5440
to implement three-phase BLDC motor control. The BLDC motor system is mainly composed of
the power circuit, MCU control circuit, motor driving circuit and voltage/current detection circuit,
which will be introduced in detail in the hardware block diagram section.
Functional Description
All necessary and important functions required for brushless motor driving are integrated in the
HT66FM5440 device and are coordinated by the BLDC motor control circuit. These functions
include a 10-bit motor dedicated PWM, mask function, Hall sensor decoder and motor protection
function, which combined with the OCP, capture timer, etc., provide the advantage of fast system
protection. From the perspective of a control system, the main points of each function will be
explained in the following.
Hall Sensor/Sensorless
For brushless motor operation, it is necessary to know the rotor position in order to provide correct
operation phase. There are two methods to obtain the rotor position, which are determined by the
actual solution: the Hall sensor solution (Hall IC & Hall component) or the sensorless solution.
If using the Hall IC, the present Hall sensor information can be obtained from the H1~H3 pins.
However for the sensorless or Hall component solution, the rotor position can only obtained after the
necessary processing by the internal three comparators. Refer to the Hall Sensor Noise Filter Block
Diagram for more details.
Square-wave / Sine-wave Driving
The square-wave driving and the sine-wave driving are different in the phase change algorithm and
more importantly in the PWM configuration. The mask function is composed of mask circuit, dead-
time circuit and polarity control circuit, which combined with the motor dedicated 10-bit PWM can
implement square-wave driving. When the hardware mask mode is selected, square-wave driving
phase change logic is implemented by the Hall sensor decoder, users can detect the signals on the
H1~H3 pins for automatic phase change or use program for phase change. When the software mask
mode is selected, users can flexibly configure the PWM signals on the motor control dedicated I/
O ports and use the PWM center-align mode and dead-time control to implement PWM outputs
required for sine-wave driving.