AN2514 Freescale Semiconductor / Motorola, AN2514 Datasheet - Page 6

• Manufacturer Part Number: AN2514
• Description: 3-Phase Sine Wave Generator TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

AN2514/D
6
PWM periods per reload of new values – are also read at each reload, so these
parameters can be changed during run time. Conversely, the dead-time (DT)
and the minimum pulse width (MPW) are not supposed to be changed during
run time. The CPU notifies the TPU that the new reload values are prepared by
setting the LD_OK parameter. The TPU notifies the CPU that the reload values
have been read and new values can be written by clearing the LD_OK
parameter.
The TPU function rotates the Stator Reference Voltage Vector by dTheta angle
each period. So the TPU can drive the motor with constant amplitude and
constant speed independently of the CPU. The CPU can adjust the Ampl
parameter to change the Stator Reference Voltage Vector amplitude and the
dTheta parameter to change the rotation speed. The CPU can also set the
absolute value of Stator Reference Voltage Vector angle Theta. To notify the
TPU that the Theta parameter should be loaded instead of using the buffered
value, the CPU must set LD_OK = $8001 instead of $0001.
The following equations describe how the 3-phase sine wave PWM signal high-
times ht
calculated:
The function cos is calculated using a table of 32 values from the first quadrant
of one cosine wave period. The function parameter is mirrored in the first
quadrant. The function value is obtained by linear interpolation between the two
closest table values.
calculation. The maximum error is 7 in the amplitude range <–32768, 32767>,
that is 0.021%.
3-Phase Sine Wave Generator TPU Function Set (3Sin)
Theta
s
s
s
A
B
Freescale Semiconductor, Inc.
C
For More Information On This Product,
cos
cos
A
, ht
s
Theta
Theta
B
Theta
A
, ht
Go to: www.freescale.com
C
s
B
and transition times t
dTheta
Figure 2
120
shows the error of the cosine function value
low-high
and t
high-low
of each channel are
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