mpc5604e Freescale Semiconductor, Inc, mpc5604e Datasheet - Page 37

• Manufacturer Part Number: mpc5604e
• Description: Mpc5604e Microcontroller Data Sheet
• Manufacturer: Freescale Semiconductor, Inc

3.14
The device provides a 10-bit Successive Approximation Register (SAR) Analog-to-Digital Converter.
3.14.1
To preserve the accuracy of the A/D converter, it is necessary that analog input pins have low AC impedance. Placing a capacitor
with good high frequency characteristics at the input pin of the device can be effective: the capacitor should be as large as
possible, ideally infinite. This capacitor contributes to attenuating the noise present on the input pin; further, it sources charge
during the sampling phase, when the analog signal source is a high-impedance source.
A real filter can typically be obtained by using a series resistance with a capacitor on the input pin (simple RC filter). The RC
filtering may be limited according to the value of source impedance of the transducer or circuit supplying the analog signal to
Freescale Semiconductor
code out
Analog-to-Digital Converter (ADC) electrical characteristics
Input impedance and ADC accuracy
1023
1022
1021
1020
1019
1018
Offset Error OSE
7
6
5
4
3
2
1
0
1
2
Figure 9. ADC characteristics and error definitions
3
Preliminary—Subject to Change Without Notice
4
1 LSB (ideal)
MPC5604E Microcontroller Data Sheet, Rev. 2
5
6
(4)
(3)
7
(2)
(5)
V
1017 1018 1019 1020 1021 1022 1023
in(A)
(LSB
ideal
(1)
(1) Example of an actual transfer curve
(2) The ideal transfer curve
(3) Differential non-linearity error (DNL)
(4) Integral non-linearity error (INL)
(5) Center of a step of the actual transfer curve
Offset Error OSE
)
1 LSB ideal = V
DD_ADC
Gain Error GE
/ 1024
Electrical characteristics
37