MC3S12RG128 Datasheet, PDF (519/546 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
A.2.3.3 Current injection
There are two cases to consider.
1. A current is injected into the channel being converted. The channel being stressed has conversion
values of $3FF ($FF in 8-bit mode) for analog inputs greater than VRH and $000 for values less
than VRL unless the current is higher than specified as disruptive conditions.
2. Current is injected into pins in the neighborhood of the channel being converted. A portion of this
current is picked up by the channel (coupling ratio K), This additional current impacts the accuracy
of the conversion depending on the source resistance.
The additional input voltage error on the converted channel can be calculated as V_ERR = K * R_S *
I_INJ, with I_INJ being the sum of the currents injected into the two pins adjacent to the converted
channel.
Table A-11. ATD Electrical Characteristics
Conditions are shown in Table A-4 unless otherwise noted
Num C
Rating
Symbol
Min
Typ
Max
Unit
1
C Max input Source Resistance
2
T Total Input Capacitance
Non Sampling
Sampling
3
C Disruptive Analog Input Current
4
C Coupling Ratio positive current injection
5
C Coupling Ratio negative current injection
R_S
C_INN
C_INS
I_NA
K_p
K_n
−
−
−2.5
1
KΩ
pF
10
22
2.5
mA
10^-4
A/A
10^-2
A/A
A.2.4 ATD accuracy (5V Range)
Table A-12 specifies the ATD conversion performance excluding any errors due to current injection, input
capacitance and source resistance.
Table A-12. 5V ATD Conversion Performance
Conditions are shown in Table A-4 unless otherwise noted
V_REF = V_RH - V_RL = 5.12V. Resulting to one 8 bit count = 20mV and one 10 bit count = 5mV
f_ATDCLK = 2.0MHz
Num C
Rating
Symbol
Min
Typ
Max
Unit
1
P 10-Bit Resolution
2
P 10-Bit Differential Nonlinearity
3
P 10-Bit Integral Nonlinearity
4
P 10-Bit Absolute Error¹
5
P 8-Bit Resolution
6
P 8-Bit Differential Nonlinearity
7
P 8-Bit Integral Nonlinearity
8
P 8-Bit Absolute Error¹
LSB
−
5
−
mV
DNL
–1
−
+1
Counts
INL
–2.5
±1.5
+2.5 Counts
AE
−3
±2
3
Counts
LSB
−
20
−
mV
DNL
–0.5
−
0.5
Counts
INL
–1.0
±0.5
1.0
Counts
AE
−1.5
±1.0
1.5
Counts
MC3S12RG128 Data Sheet, Rev. 1.05
Freescale Semiconductor
519