QADC64E Enhanced Mode Operation
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
14-67
Since the sample amplifier is powered by V
DDA
and V
SSA
, it can accurately transfer input signal levels up
to but not exceeding V
DDA
and down to but not below V
SSA
. If the input signal is outside of this range, the
output from the sample amplifier is clipped.
In addition, V
RH
and V
RL
must be within the range defined by V
DDA
and V
SSA
. As long as V
RH
is less than
or equal to V
DDA
and V
RL
is greater than or equal to V
SSA
and the sample amplifier has accurately
transferred the input signal, resolution is ratiometric within the limits defined by V
RL
and V
RH
. If V
RH
is
greater than V
DDA
, the sample amplifier can never transfer a full-scale value. If V
RL
is less than V
SSA
, the
sample amplifier can never transfer a zero value.
shows the results of reference voltages outside the range defined by V
DDA
and V
SSA.
At the
top of the input signal range, V
DDA
is 10 mV lower than V
RH
. This results in a maximum obtainable 10-bit
conversion value of 0x3FE. At the bottom of the signal range, V
SSA
is 15 mV higher than V
RL
, resulting in
a minimum obtainable 10-bit conversion value of three.
Figure 14-48. Errors Resulting from Clipping
14.6.3.1
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 V
DD
/V
SS
signal pair. This applies to
analog sub-modules also. The distribution of power and ground is equally important.
QADC64E Clipping
0
.020
5.100
5.110
Input in Volts (V
RH
= 5.12 V, V
RL
= 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
xa
d
e
ci
ma
l)
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...