MC3PHAC Motorola, MC3PHAC Datasheet - Page 20

• Manufacturer Part Number: MC3PHAC
• Description: 3-Phase AC Motor Controller
• Manufacturer: Motorola

MC3PHAC/D
Grounding Considerations
Power-Up/Power-Down
Operation
20
Printed circuit board layout is an important design consideration. In particular,
ground planes and how grounds are tied together influence noise immunity. To
maximize noise immunity, it is important to get a good ground plane under the
MC3PHAC. It is also important to separate analog and digital grounds. That is
why, shown on the schematics, there are two ground designations, analog
ground is marked with an A and other grounds are digital grounds. GND is the
digital ground plane and power supply return. GNDA is the analog circuit
ground. They are both the same reference voltage, but are routed separately,
and tie together at only one point.
When power is applied or removed, it is important that the inverter’s top and
bottom output transistors in the same phase are not turned on simultaneously.
Since logic states are not always defined during power-up, it is important to
ensure that all power transistors remain off when the controller’s supply voltage
is below its normal operating level. The MC3PHAC’s PWM module outputs
make this easy by switching to a high impedance configuration whenever the
5-volt supply is below its specified minimum.
The user should use pullup or pulldown resistors on the output of the
MC3PHAC’s PWM outputs to ensure during power-up and power-down, that
the inverter’s drive inputs are at a known, turned off, state.
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.
Freescale Semiconductor, Inc.
For More Information On This Product,
3-Phase AC Motor Controller
Go to: www.freescale.com
MOTOROLA