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This application note describes the design of a 3-phase Table of Contents
Brushless DC (BLDC) motor drive based on Freescale’s
PowerPC MPC5554 microcontroller. The application
design takes advantage of the Enhanced Time Processing
Unit (eTPU) module, which is used as a motor control
co-processor. The eTPU completely handles the motor
control processing, eliminating the microprocessor
overhead for other duties.
BLDC motors are very popular in a wide array of
applications. Compared to a DC motor, the BLDC motor
uses an electric commutator, replacing the mechanical
commutator and making it more reliable than the DC
motor. In BLDC motors, rotor magnets generate the
rotor’s magnetic flux, allowing BLDC motors to achieve
higher efficiency. Therefore, BLDC motors may be used
in high-end white goods (refrigerators, washing
machines, dishwashers, etc.), high-end pumps, fans, and
other appliances that require high reliability and
efficiency.
The concept of the application is to create a speed-closed
loop BLDC driver using a Hall position sensor. It serves
as an example of a BLDC motor control system design
using a Freescale microprocessor with the eTPU. It also illustrates the usage of dedicated motor control eTPU functions that are included in the DC motor control
eTPU function set.
This application note also includes basic motor theory, system design concept, hardware implementation,
and microprocessor and eTPU software design, including the FreeMASTER visualization tool.
User Interface
The application is interfaced by the following:
• ON/OFF switch on the Interface Board with UNI-3
• Up/Down buttons on the Interface Board with UNI-3, or FreeMASTER running on a PC
connected to the MPC5554DEMO via an RS232 serial cable.
The ON/OFF switch affects the application state and enables and disables the PWM phases. When the
switch is in the off-position, no voltage is applied to the motor windings. When the ON/OFF switch is in the on-position, the motor speed can be controlled either by the Up and Down buttons on the Interface
Board, or by the FreeMASTER on the PC. The FreeMASTER also displays a control page, real-time
values of application variables, and their time behavior using scopes.
FreeMASTER software was designed to provide an application-debugging, diagnostic, and demonstration
tool for the development of algorithms and applications. It runs on a PC connected to the MPC5554DEMO
via an RS232 serial cable. A small program resident in the microprocessor communicates with the
FreeMASTER software to return status information to the PC and process control information from the
PC. FreeMASTER software, executing on a PC, uses part of Microsoft Internet Explorer as the user
interface.
Note, that FreeMASTER version 1.2.31.1 or higher is required. The FreeMASTER application can be
downloaded from http://www.freescale.com. For more information about FreeMASTER, refer to
Reference 5.
3.3 Hardware Implementation and Application Setup
As previously stated, the application runs on the MPC5554 family of PowerPC microprocessors using the
following:
• MPC5554DEMO
• Interface Board with UNI-3
• 33395 Evaluation Motor Board
• Pittman N2311 3-phase BLDC motor
• Power Supply, 12V DC, minimum 2.7 Amps
Figure 11 shows the connection of these parts. All system parts are supplied by Freescale and documented
according to references.
3.3.1 PowerPC MPC5554 Evaluation Board (MPC5554DEMO)
This board is not intended to be a full evaluation board for the MPC5554, but shows a minimal system for
learning about the new MPC5500 family of product.
The FLASH memory placed on the MPC5554 has three address spaces. Low and mid address spaces are
256-Kbytes and high address spaces is 1.5 Mbyte in size. It gives a total memory space of 2Mbytes.
Flashing the MPC5554DEMO
The eSys Flasher utility can be used for programming code into the FLASH memory on the
MPC5554DEMO. Check for correct setting of switches and jumpers.The flashing procedure is as follows:
1. Run Metrowerks MPC55xx V1.5b2 and open the project. Choose the Intflash target and compile
the application. A file simple_eflash.elf.S19, which will be loaded into FLASH memory, is created
in the project directory bin.
2. Run the eSysFlasher application. In the Target Configuration window select the type of the BDM
Communication as P&E Wiggler. Click OK to close the window.
3. Go to the Program section by clicking the “Program Flash” button (see Figure 12). Select the
Binary Image, set Address as 0x0 and check the “Verify after program” option (see Figure 13).
Press the “Program” and select intflash.bin file. Finally, press “Open” button at the bottom of the
window to start loading the code into the FLASH memory.
4. If the code has been programmed correctly, remove the BDM interface and push the RESET
button on the MPC5554Demo. The application should now run from the FLASH.