TRK-USB-MPC5643L Freescale Semiconductor, TRK-USB-MPC5643L Datasheet - Page 97

• Manufacturer Part Number: TRK-USB-MPC5643L
• Description: Development Boards & Kits - Other Processors StarTrakMiniUSG MPC5643L
• Manufacturer: Freescale Semiconductor

Specifications of TRK-USB-MPC5643L

• Rohs: yes
• Product: Starter Kits
• Tool Is For Evaluation Of: MPC5643L
• Core: Five Stage Pipeline
• Interface Type: LIN, DSPI
• Operating Supply Voltage: 3 V to 3.6 V
• Data Bus Width: 32 bit, 64 bit
• Description/function: Starter Kit for MPC5643L
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• For Use With: MPC5643L

Calling f
according to the Nyquist theorem the conversion rate f
than or at least equal to twice the conversion period (T
which is just a portion of it, even when fixed channel continuous conversion mode is selected (fastest conversion rate at a
specific channel): in conclusion it is evident that the time constant of the filter R
sampling time T
sampling switch is closed.
The considerations above lead to impose new constraints on the external circuit, to reduce the accuracy error due to the voltage
drop on C
voltage on C
From this formula, in the worst case (when V
half a count, a constraint is evident on C
Freescale Semiconductor
0
S
the bandwidth of the source signal (and as a consequence the cut-off frequency of the anti-aliasing filter, f
; from the two charge balance equations above, it is simple to derive
S
:
S
, so the charge level on C
Anti-Aliasing Filter (f
Analog Source Bandwidth (V
Figure 10. Spectral representation of input signal
f
f
0
F
MPC5643L Microcontroller Data Sheet, Rev. 8.1
F
F
value:
= RC Filter pole)
S
Noise
cannot be modified by the analog signal source during the time in which the
A
----------- -
V A2
V A
is maximum, that is for instance 5 V), assuming to accept a maximum error of
f
f
A
)
=
C
C
must be at least 2f
C F
). Again the conversion period T
------------------------------------------------------- -
C P1
C P1

8192
+
Sampled Signal Spectrum (f
C P2
T
f
2 f
F
+
C
 f
0
2 R
C P2

f
0
C S
(Anti-aliasing Filtering Condition)
+
C
(Nyquist)
F
C F
C
f
0
+
F
0
C F
(Conversion Rate vs. Filter Pole)
; it means that the constant time of the filter is greater
+
C S
Equation 11
F
C
C
F
= conversion Rate)
is definitively much higher than the
f
C
C
is longer than the sampling time T
between the ideal and real sampled
Electrical characteristics
f
F
Eqn. 12
),
Eqn. 11
97
S
,