mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 1254

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Appendix A Electrical Characteristics
1
2
A.2.2
Three factors — source resistance, source capacitance and current injection — have an influence on the
accuracy of the ATD.
A.2.2.1
Due to the input pin leakage current as specified in
there will be a voltage drop from the signal source to the ATD input. The maximum source resistance R
specifies results in an error of less than 1/2 LSB (2.5 mV) 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
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
1254
Conditions are shown in
Num C
Full accuracy is not guaranteed when differential voltage is less than 3.15 V
The minimum time assumes a final sample period of 2 ATD clocks cycles while the maximum time assumes a final sample
period of 16 ATD clocks.
1
2
3
4
5
6
7
8
D Reference potential
C Differential reference voltage
D ATD clock frequency
D ATD 10-bit conversion period
D ATD 8-bit conversion period
D Recovery time (V
P Reference supply current 2 ATD blocks on
P Reference supply current 1 ATD block on
Factors Influencing Accuracy
Low
High
Clock cycles
Conv, time at 2.0 MHz ATD clock f
Clock cycles
Conv, time at 2.0 MHz ATD clock f
Source Resistance
Source Capacitance
Table A-4
2
2
DDA
= 5.0 Volts)
Table A-13. ATD Operating Characteristics 3.3V
unless otherwise noted, Supply Voltage 3.15V < VDDA < 3.6V
Rating
1
MC9S12XDP512 Data Sheet, Rev. 2.17
ATDCLK
ATDCLK
Table A-7
f
1024 * (C
N
V
T
Symbol
N
f
T
ATDCLK
RH
CONV10
CONV10
CONV8
CONV8
t
I
I
V
V
REC
REF
REF
RH
RL
-V
in conjunction with the source resistance
RL
INS
–C
V
V
3.15
DDA
Min
INN
0.5
14
12
SSA
—
—
—
7
6
/2
).
Typ
3.3
—
—
—
—
—
—
—
—
—
—
Freescale Semiconductor
V
0.500
0.250
V
Max
DDA
3.6
2.0
28
14
26
13
20
DDA
/2
Cycles
Cycles
MHz
Unit
mA
mA
V
V
V
s
s
s
S