AN2518 Freescale Semiconductor / Motorola, AN2518 Datasheet - Page 5

• Manufacturer Part Number: AN2518
• Description: 3-Phase Sine Wave Generator - 3 outputs version - XOR version TPU Function Set
• Manufacturer: Freescale Semiconductor / Motorola

Detailed Function Description
3-Phase Sine Wave
Generator – 3
outputs version –
XOR version – R
channels
(3Sin3Xor_R)
and 3-Phase Sine
Wave Generator – 3
outputs version –
XOR version – T
channels
(3Sin3Xor_T)
MOTOROLA
3-Phase Sine Wave Generator – 3 outputs version – XOR version TPU Function Set (3Sin3Xor)
The 3Sin3Xor_R and 3Sin3Xor_T TPU functions work together to generate 3
pairs of XOR gate inputs. The XOR gate outputs then produce a 3-channel 3-
phase center-aligned PWM signal. Unlike the 3Sin, the generated signals are
not top-bottom pairs with dead-times but only top-like signals without dead-
times. In order to charge the bootstrap transistors, the PWM signals start to run
1.6ms after their initialization (at 20MHz TCR1 clock). The functions generate
signals corresponding to Reference Voltage Vector Amplitude of 0 (50% duty-
cycle) until the first reloaded values are processed.
The CPU controls the PWM output by setting the TPU parameters. The Stator
Reference Voltage Vector Amplitude Ampl, the Stator Reference Voltage
Vector angle Theta (32-bit) and the angle increment dTheta (32-bit), can be
adjusted during run time. The PWM period T and the prescaler – the number of
PWM periods per reload of new values – are also read at each reload, so these
parameters can 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
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.
Theta
s
s
s
A
B
Freescale Semiconductor, Inc.
C
For More Information On This Product,
cos
cos
A
, ht
s
Theta
Theta
Theta
A
B
, 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
trans
of each channel are calculated:
Detailed Function Description
AN2518/D
5