MC9S12A256B ETC, MC9S12A256B Datasheet - Page 98

• Manufacturer Part Number: MC9S12A256B
• Description: device made up of standard HCS12 blocks and the HCS12 processor core
• Manufacturer: ETC

MC9S12DP256B Device User Guide — V02.14
specifies results in an error of less than 1/2 LSB (2.5mV) at the maximum leakage current. If device or
operating conditions are less than worst case or leakage-induced error is acceptable, larger values of source
resistance is allowed.
A.2.2.2 Source Capacitance
When sampling an additional internal capacitor is switched to the input. This can cause a voltage drop due
to charge sharing with the external and the pin capacitance. For a maximum sampling error of the input
voltage 1LSB, then the external filter capacitor, C
A.2.2.3 Current Injection
There are two cases to consider.
Conditions are shown in Table A-4 unless otherwise noted
Num C
1
2
3
4
5
1. A current is injected into the channel being converted. The channel being stressed has conversion
2. Current is injected into pins in the neighborhood of the channel being converted. A portion of this
98
C Max input Source Resistance
C Disruptive Analog Input Current
C Coupling Ratio positive current injection
C Coupling Ratio negative current injection
T
values of $3FF ($FF in 8-bit mode) for analog inputs greater than V
V
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
I
channel.
INJ
RL
Total Input Capacitance
Non Sampling
Sampling
, with I
unless the current is higher than specified as disruptive condition.
INJ
being the sum of the currents injected into the two pins adjacent to the converted
Rating
Table A-9 ATD Electrical Characteristics
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
f
1024 * (C
Symbol
C
C
I
R
K
K
NA
INN
INS
S
p
n
INS
Min
-2.5
- C
-
INN
RH
).
and $000 for values less than
Typ
-
ERR
Max
10
10
2.5
10
22
1
-4
-2
= K * R
Unit
mA
A/A
A/A
K
pF
S
*