AN1857 Freescale Semiconductor / Motorola, AN1857 Datasheet - Page 5

• Manufacturer Part Number: AN1857
• Description: A 3-Phase ac Induction Motor Control System Based on the MC68HC908MR32
• Manufacturer: Freescale Semiconductor / Motorola

AN1857
MOTOROLA
One of the most important features of the PWMMC is its ability to “shut
itself down” when a system fault is detected. When dealing with a system
that potentially could have hundreds of amps of peak current, reacting to
faults such as overcurrent or overvoltage conditions is an absolute
necessity. Fault protection is discussed here first. We then work our way
from the outputs of the PWM inward. A discussion of the inputs to the
PWM follows.
The six outputs of the PWMMC generator can be configured as
individual pulse-width modulated signals where each output can be
controlled as an independent output. Another option is to configure the
outputs in pairs, with the outputs complementary or not, so driving
complementary top and bottom transistors on a power stage becomes
an easy task. The outputs of the PWMMC are capable of sinking up to
20 mA. That drive capability allows for direct drive of optocouplers
without the need of additional drivers.
To prevent erroneous signals from being output from the PWMMC
module while loading new values, the bulk of the registers are double
buffered and new output is inhibited until a bit in a PWM control register,
load okay (LDOK), is set, indicating it is okay to output the new values.
Freescale Semiconductor, Inc.
PRESCALER
1, 2, 4,O R 8
For More Information On This Product,
COMPARATORS
GENERATORS
Go to: www.freescale.com
MOTOR CURRENT POLARITIES
REGISTERS
BUFFERED
Figure 2. PWMMC Module Block Diagram
DOUBLE
PWM
COUNTER
UP/DOWN
OR
CORRECTION
PRESCALER
DISTORTION
1, 2, 4, OR 8
INSERTION
CONTROL
CONTROL
OUTPUT
SELECT
DIRECT
MODE
DEAD-
PWM
TIME
SYSTEM FAULTS
MC68HC908MR32 Pulse-Width Modulator
PARTITIONING
PROTECTION
PWM RELOAD
AND INTERRUPT
SELECT
FAULT
FAULT
FAULT
MODE
INTERRUPTS
POLARITY
CONTROL
CURRENT
DRIVERS
OUTPUT
HIGH
Application Note
PWM1
PWM2
PWM3
PWM4
PWM5
PWM6
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