AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 4

• Manufacturer Part Number: AN1914
• Description: 3-Phase BLDC Motor Control with Sensorless Back EMF Zero Crossing Detection Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

Target Motor Theory
3.
3.1 BLDC Motor Targeted by This Application
4
The Quadrature Timer provides the capability to precisely control the key sensorless BLDC events by
providing the time base for zero crossing events and the output compare function for scheduling the
commutation events.
Dual Analog-to-Digital Converter (ADC) modules—four inputs on each has the following feature set:
The Analog-to-Digital Converter is utilized to measure DC-bus voltage, DC-Bus current and the
power module temperature. Its Hi/Lo level detection capability provides automatic detection of the
over/under-voltage, over-current and over temperature protection (serviced in associated ISR).
The Brushless DC motor (BLDC motor) is also referred to as an electronically commuted motor. There
are no brushes on the rotor and the commutation is performed electronically at certain rotor positions.
The stator magnetic circuit is usually made from magnetic steel sheets. The stator phase windings are
inserted in the slots (distributed winding) as shown in
magnetic pole. The magnetization of the permanent magnets and their displacement on the rotor are
chosen such a way that the Back-EMF (the voltage induced into the stator winding due to rotor
movement) shape is trapezoidal. This allows the three phase voltage system (see
rectangular shape, to be used to create a rotational field with low torque ripples.
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Target Motor Theory
Set, clear, or toggle output capture action
Pulse Width Modulator (PWM) signal generation
Programmable clock sources and frequencies, including external clock
Eight total analog inputs
12-bit range
Monotonic over entire range with no missing codes
First channel on each ADC can be swapped with the alternate ADC
Can perform two simultaneous analog-to-digital conversions
Conversion time = 1.25 us
Contains programmable zero offset register
Generates interrupt on completion of conversion
Optional conversion interrupt is asserted when the analog voltage level exceeds, or
falls below, the value contained in the zero offset register
Output is in two’s complement or unsigned formats
DSP56F80x MC PWM Module in Motor Control Applications
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Figure 3-1
or it can be wound as one coil on the
Figure
3-2), with a