mc3phacvp Freescale Semiconductor, Inc, mc3phacvp Datasheet - Page 16

• Manufacturer Part Number: mc3phacvp
• Description: Mc3phac Motor Control Unit
• Manufacturer: Freescale Semiconductor, Inc

Operation
Operation
The MC3PHAC motor controller will operate in two modes. The first is standalone operation, whereby the
MC3PHAC can be used without any intervention from an external personal computer. In standalone
mode, the MC3PHAC is initialized by passive devices connected to the MC3PHAC and input to the
system at power-up/reset time. In standalone mode, some parameters continue to be input to the system
as it operates. Speed, PWM frequency, bus voltage, and acceleration parameters are input to the system
on a real-time basis.
The second mode of operation is called PC master software mode.That operational mode requires the
use of a personal computer and PC master software executing on the personal computer, communicating
with the MC3PHAC, or a microcontroller emulating PC master software commands. All command and
setup information is input to the MC3PHAC via the PC host.
Standalone Operation
If the VBOOST_MODE pin is high when the MC3PHAC is powered up, or after a reset, the MC3PHAC
enters standalone mode. In this mode of operation, the functionality of many of the MC3PHAC pins
change so that the device can control a motor without requiring setup information from an external master.
When operated in standalone mode, the MC3PHAC will drive certain pins corresponding to parameters
which must be specified, while simultaneously monitoring the response on other pins.
In many cases, the parameter to be specified is represented as an analog voltage presented to the
MUX_IN pin, while certain other pins are driven low. In so doing, the MC3PHAC can accommodate an
external analog mux which will switch various signals on the MUX_IN pin when the signal select line goes
low. All signals must be in a range between 0 V and V
. As an economical alternative, an external
REF
passive network can be connected to each of the parameter select output pins and the MUX_IN pin, as
shown in
Figure
8.
The Thevenin equivalent impedance of this passive network as seen by the MUX_IN pin is very important
and should be in the range of 5 kΩ to 10 kΩ. If the resistance is too high, leakage current from the
input/output (I/O) pins will cause an offset voltage that will affect the accuracy of the reading. If the
resistance is too low, the parameter select pins will not be able to sink the required current for an accurate
reading. Using a pullup resistor value of 6.8 kΩ (as indicated in
Figure
8), the resulting value for each
parameter as a function of the corresponding pulldown resistor value is shown in
Figure
9,
Figure
10,
Figure
11, and
Table
4.
The START input pin is debounced internally and a switch can be directly accommodated on this pin. The
input is level sensitive, but a logic 1 level must exist on the pin before a logic 0 level will be processed as
a start signal. This will prevent an accidental motor startup in the event of the MC3PHAC being powered
up, where the switch was left in the start position.
The FWD input pin is debounced internally and can directly accommodate a switch connection. The input
is also level sensitive.
Figure 8
shows the jumper arrangement connected to the PWMPOL_BASEFREQ input pin. For proper
operation, one and only one jumper connection can be made at any given time.
Table 3
shows the polarity
and base frequency selections as a function of the jumper connection.
MC3PHAC Monolithic Intelligent Motor Controller, Rev. 2
16
Freescale Semiconductor