mc9s12hz256v2 Freescale Semiconductor, Inc, mc9s12hz256v2 Datasheet - Page 633

• Manufacturer Part Number: mc9s12hz256v2
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

A.2.2.2
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
There are two cases to consider.
Freescale Semiconductor
Conditions are shown in
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
C Max input Source Resistance
C Disruptive Analog Input Current
C Coupling Ratio positive current injection
C Coupling Ratio negative current injection
T Total Input Capacitance
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
Non Sampling
Sampling
, with I
unless the current is higher than specified as disruptive condition.
Source Capacitance
Current Injection
INJ
Table A-4
being the sum of the currents injected into the two pins adjacent to the converted
Rating
unless otherwise noted
Table A-9. ATD Electrical Characteristics
MC9S12HZ256 Data Sheet, Rev. 2.05
f
1024 * (C
Symbol
C
C
I
R
K
K
NA
INN
INS
S
p
n
INS
–2.5
– C
Min
–
INN
RH
).
Appendix A Electrical Characteristics
and $000 for values less than
Typ
–
ERR
10
10
Max
2.5
10
22
1
–4
–2
= K * R
Unit
A/A
A/A
mA
K
pF
S
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