AN1915D Freescale Semiconductor / Motorola, AN1915D Datasheet - Page 3

• Manufacturer Part Number: AN1915D
• Description: 3-Phase BLDC Motor Control with Quadrature Encoder using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

MOTOROLA
The BLDC motor control utilizes the PWM block set in the complementary PWM mode (for control in
complementary mode - see chapter 3.1.2 Complementary Switching of Power Transistors), permitting
the generation of control signals for all switches of the power stage, with inserted deadtime. The PWM
outputs can be controlled separately by software, where setting the control signal to logical 0 or 1
enables/disables control signal. The next key feature, which is very useful in BLDC motor control, is
the channel swap function. The swap function allows the immediate change of top and bottom
transistors in the phase. These functions allow the rotor commutation and speed control to be split into
two independent program parts. The state of the control signals can be changed immediately when
required by the motor position (phase commutation) without changing the content of the PWM value
registers. These changes can be accomplished asynchronously to the PWM duty cycle update.
The Quad Timer is an extremely flexible module, providing all of the required services related to time
events. It has the following features:
The BLDC motor application utilizes one channel of the Quad Timer module counting in quadrature
mode. It enables rotor position sensing using the Quadrature Encoder. The second channel of the Quad
Timer module is set to generate a time base for the speed controller.
The Quadrature Decoder is a module that provides decoding of position signals from a Quadrature
Encoder mounted on a motor shaft. It has the following features:
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Complementary channel operation
Deadtime insertion
Separate top and bottom pulse width correction via current status inputs or software
Separate top and bottom polarity control
Edge-aligned or center-aligned PWM signals
15 bits of resolution
Half-cycle reload capability
Integral reload rates from 1 to 16
Individual software-controlled PWM outputs
Mask and Swap of PWM outputs
Programmable fault protection
Polarity control
20-mA current sink capability on PWM pins
Write-protectable registers
Each timer module consists of four 16-bit counters/timers
Count up/down
Counters are cascadable
Programmable count modulo
Max count rate equals peripheral clock/2 when counting external events
Max count rate equals peripheral clock when using internal clocks
Count once or repeatedly
Counters are preloadable
Counters can share available input pins
Each counter has a separate prescaler
Each counter has capture and compare capability
3-Phase BLDC Motor Control with Quadrature Encoder
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Motorola DSP Advantages and Features
3