QADC64E Legacy Mode Operation
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
13-69
Figure 13-50. Errors Resulting from Clipping
13.7.3.1
Analog Supply Filtering and Grounding
Two important factors influencing performance in analog integrated circuits are supply filtering and
grounding. Generally, digital circuits use bypass capacitors on every VDD/VSS signal pair. This applies
to analog sub-modules also. The distribution of power and ground is equally important.
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.
For example, 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.
Grounding is the most important factor influencing analog circuit performance in mixed signal systems (or
in stand-alone analog systems). Care must be taken to not 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.
QADC64E CLIPPING
0
.020
5.100
5.110
Input in Volts (VRH = 5.120,
= 0 V)
1
2
3
4
5
6
7
8
3FA
3FB
3FC
3FD
3FE
3FF
.010
.030
5.120
5.130
1
0
-Bi
t
R
e
su
lt
(H
e
x
a
d
e
ci
ma
l)
V
RL
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...
