GETINFOBRIEF datasheet(19/36 Pages) FREESCALE

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Operation

MC3PHAC Monolithic Intelligent Motor Controller, Rev. 2

Freescale Semiconductor

Standalone Application Example

Figure 12 shows an application example of the MC3PHAC, configured in standalone mode. Resistor

values and jumpers have been selected to provide the following performance:

Base frequency of 60 Hz and positive PWM polarity (from Table 3)

PWM frequency resistor 3.9 k

Ω, which implies 10.582 kHz from Table 4). (5v/(3.9k + 6.8k))*3.9k =

1.82 volts

Dead-time resistor = 5.1 k

Ω, which implies 4.5 µs (from Figure 9)

Fault retry time resistor = 8.2 k

Ω, which implies 32.8 seconds (from Figure 10).

Voltage boost resistor = 12 k

Ω, which implies 25.5 percent (from Figure 11).

The wiper of the acceleration potentiometer is set at 2.5 V = 64 Hz/second acceleration rate (from

the Acceleration Control description on page 11.) The potentiometer, in this case, could have been

a resistor divider. If a resistor divider is used in place of the acceleration potentiometer, keep the

total resistance of the two resistors less than 10 k

Ω. Always use 4.7kΩ in series with the center of

the acceleration voltage divider resistors, connected to the ACCEL (pin 27) as shown in the

application example, Figure 12.

Crystal/resonator capacitor values are typical values from the manufacturer. Refer to the

manufacturers data for actual values.

PC Master Software Operation

Introduction to PC Master Host Software

The MC3PHAC is compatible with Freescale’s PC master host software serial interface protocol.

Communication occurs over an on-chip UART, on the MC3PHAC at 9600 baud to an external master

device, which may be a microcontroller that also has an integrated UART or a personal computer via a

COM port. With PC master software, an external controller can monitor and control all aspects of the

MC3PHAC operation.

When the MC3PHAC is placed in PC master software mode, all control of the system is provided through

the integrated UART, resident on the MC3PHAC. Inputs such as START, FWD, SPEED, ACCEL,

MUX_IN, and PWMPOL_BASEFREQ have no controlling influence over operation of the system. Even

though the SPEED, START, and FWD inputs are disabled while the system is in PC master software

mode, through PC master software, it is possible to monitor the state of those inputs.

The most popular master implementation is a PC, where a graphical user interface (GUI) has been

layered on top of the PC master software command protocol, complete with a graphical data display, and

an ActiveX interface. Figure 13 shows the MC3PHAC configured in PC master software mode. It is

beyond the scope of this document to describe the PC master software protocol or its implementation on

a personal computer. For further information on these topics, refer to other Freescale documents relating

to the PC master software protocol and availability of PC master host software.

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