MPC561MZP56 Freescale, MPC561MZP56 Datasheet - Page 610

• Manufacturer Part Number: MPC561MZP56
• Manufacturer: Freescale

Specifications of MPC561MZP56

• Cpu Family: MPC56x
• Device Core: PowerPC
• Device Core Size: 32b
• Frequency (max): 56MHz
• Interface Type: QSPI/SCI/SPI/UART
• Total Internal Ram Size: 32KB
• # I/os (max): 56
• Number Of Timers - General Purpose: 22
• Operating Supply Voltage (typ): 2.6/5V
• Operating Supply Voltage (max): 2.7/5.25V
• Operating Supply Voltage (min): 2.5/4.75V
• On-chip Adc: 2(32-chx10-bit)
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Mounting: Surface Mount
• Pin Count: 388
• Package Type: BGA
• Program Memory Type: ROMLess
• Program Memory Size: Not Required
• Lead Free Status / RoHS Status: Not Compliant

QADC64E Enhanced Mode Operation
Analog supplies should be isolated from digital supplies as much as possible. This necessity stems from
the higher performance requirements often associated with analog circuits. Therefore, deriving an analog
supply from a local digital supply is not recommended. However, if for economic reasons digital and
analog power are derived from a common regulator, filtering of the analog power is recommended in
addition to the bypassing of the supplies already mentioned.
Grounding is the most important factor influencing analog circuit performance in mixed signal systems (or
in stand-alone analog systems). Close attention must be paid not to introduce additional sources of noise
into the analog circuitry. Common sources of noise include ground loops, inductive coupling, and
combining digital and analog grounds together inappropriately.
The problem of how and when to combine digital and analog grounds arises from the large transients
which the digital ground must handle. If the digital ground is not able to handle the large transients, the
current from the large transients can return to ground through the analog ground. It is the excess current
overflowing into the analog ground which causes performance degradation by developing a differential
voltage between the true analog ground and the microcontroller’s ground signal. The end result is that the
ground observed by the analog circuit is no longer true ground and often ends in skewed results.
Two similar approaches designed to improve or eliminate the problems associated with grounding excess
transient currents involve star-point ground systems. One approach is to star-point the different grounds at
the power supply origin, thus keeping the ground isolated. Refer to
14-68
An RC low pass filter could be used to isolate the digital and analog supplies
when generated by a common regulator. If multiple high precision analog
circuits are locally employed (i.e., two A/D converters), the analog supplies
should be isolated from each other as sharing supplies introduces the
potential for interference between analog circuits.
MPC561/MPC563 Reference Manual, Rev. 1.2
NOTE
Figure
14-49.
Freescale Semiconductor