Motorola MC9S12GC-Family - Manual (Page 101)

Device User Guide — 9S12C128DGV1/D V01.05
101
B.4.3.3 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 B-5 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 R
S
- - 1 K
Ω
2 T
Total Input Capacitance
Non Sampling
Sampling
C
INN
C
INS
10
15 pF
3 C Disruptive Analog Input Current I
NA
-2.5 2.5 mA
4 C Coupling Ratio positive current injection K
p 10
-4 A/A
5 C Coupling Ratio negative current injection K
n 10
-2 A/A