Appendix A Electrical Characteristics
MC9S12XDP512 Data Sheet, Rev. 2.11
934 Freescale Semiconductor
A.2.2.3 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 condition.
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:
VERR = K * RS * IINJ
with IINJ being the sum of the currents injected into the two pins adjacent to the converted channel.
Table A-14. 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 RS—— 1K
2 T Total input capacitance
Non sampling
Sampling
CINN
CINS
10
22
pF
3 C Disruptive analog input current INA –2.5 2.5 mA
4 C Coupling ratio positive current injection Kp——10
-4 A/A
5 C Coupling ratio negative current injection Kn——10
-2 A/A