mc3phacvp Freescale Semiconductor, Inc, mc3phacvp Datasheet - Page 11
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mc3phacvp
Manufacturer Part Number
mc3phacvp
Description
Mc3phac Motor Control Unit
Manufacturer
Freescale Semiconductor, Inc
Datasheet
1.MC3PHACVP.pdf
(36 pages)
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Selectable PWM Frequency — The MC3PHAC accommodates four discrete PWM frequencies and can
be changed dynamically while the motor is running. This resistor can be a potentiometer or a fixed resistor
in the range shown in
to the MUX_IN pin while the PWMFREQ_RxD pin is being driven low.
levels on the MUX_IN pin and the associated PWM frequency for each voltage range.
Selectable PWM Dead Time — Besides being able to specify the PWM frequency, the blanking time
interval between the on states of the complementary PWM pairs can also be specified. Refer to the graph
in
standalone mode, this is done by
supplying a voltage to the MUX_IN pin while the DT_FAULTOUT pin is being driven low. In this way, dead
time can be specified with a scaling factor of 2.075 µs per volt, with a minimum value of 0.5 µs. In PC
master software mode, this value can be selected to be anywhere between 0 and 32 µs.
In both standalone and PC master software modes, the dead time value can be written only once. Further
updates of this parameter are locked out until a reset condition occurs.
Speed Control — The synchronous motor frequency can be specified in real time to be any value from
1 Hz to 128 Hz by the voltage applied to the SPEED pin. The scaling factor is 25.6 Hz per volt. This
parameter can also be controlled directly from PC master software in real time.
The SPEED pin is processed by a 24-bit digital filter to enhance the speed stability in noisy environments.
This filter is only activated in standalone mode.
Acceleration Control — Motor acceleration can be specified in real time to be in the range from 0.5
Hz/second, ranging to 128 Hz/second, by the voltage applied to the ACCEL pin. The scaling factor is 25.6
Hz/second per volt. This parameter can also be controlled directly from PC master software in real time.
Voltage Profile Generation — The MC3PHAC controls the motor voltage in proportion to the specified
frequency, as indicated in
An ac motor is designed to draw a specified amount of magnetizing current when supplied with rated
voltage at the base frequency. As the frequency decreases, assuming no stator losses, the voltage must
decrease in exact proportion to maintain the required magnetizing current. In reality, as the frequency
decreases, the voltage drop in the series stator resistance increases in proportion to the voltage across
the magnetizing inductance. This has the effect of further reducing the voltage across the magnetizing
inductor, and consequently, the magnetizing current. A schematic representation of this effect is
Freescale Semiconductor
Figure 9
for the resistance value versus dead time.
Table 4. MUX_IN Resistance Ranges and Corresponding PWM Frequencies
The PWM frequencies are based on a 4.00 MHz frequency applied to the
oscillator input.
Table
Voltage Input
1.5 to 2.25 V
2.75 to 3.5 V
Figure
0 to 1 V
4 to 5 V
MC3PHAC Monolithic Intelligent Motor Controller, Rev. 2
4. In standalone mode, the PWM frequency is specified by applying a voltage
5.
NOTE
Figure 9
assumes a 6.8 kΩ
PWM Frequency
Table 4
10.582 kHz
15.873 kHz
21.164 kHz
5.291 kHz
shows the required voltage
±
5% pullup resistor. In
Features
11