MC9S12A256B ETC, MC9S12A256B Datasheet - Page 97

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

A.2 ATD Characteristics
This section describes the characteristics of the analog to digital converter.
A.2.1 ATD Operating Characteristics
The Table A-8 shows conditions under which the ATD operates.
The following constraints exist to obtain full-scale, full range results:
V
beyond the power supply levels that it ties to. If the input level goes outside of this range it will effectively
be clipped.
A.2.2 Factors influencing accuracy
Three factors - source resistance, source capacitance and current injection - have an influence on the
accuracy of the ATD.
A.2.2.1 Source Resistance:
Due to the input pin leakage current as specified in Table A-6 in conjunction with the source resistance
there will be a voltage drop from the signal source to the ATD input. The maximum source resistance R
Conditions are shown in Table A-4 unless otherwise noted
Num C
NOTES:
1. Full accuracy is not guaranteed when differential voltage is less than 4.50V
2. The minimum time assumes a final sample period of 2 ATD clocks cycles while the maximum time assumes a final sample
SSA
1
2
3
4
5
6
7
8
period of 16 ATD clocks.
D
C Differential Reference Voltage
D ATD Clock Frequency
D
D
D Recovery Time (V
P
P
V
Reference Potential
ATD 10-Bit Conversion Period
ATD 8-Bit Conversion Period
RL
Reference Supply current 2 ATD blocks on
Reference Supply current 1 ATD block on
V
IN
Conv, Time at 2.0MHz ATD Clock f
Conv, Time at 2.0MHz ATD Clock f
V
RH
DDA
=5.0 Volts)
Rating
Table A-8 ATD Operating Characteristics
V
Freescale Semiconductor, Inc.
DDA
For More Information On This Product,
1
This constraint exists since the sample buffer amplifier can not drive
Go to: www.freescale.com
Clock Cycles
Clock Cycles
ATDCLK
ATDCLK
High
Low
2
2
V
N
T
Symbol
N
f
T
ATDCLK
RH
CONV10
CONV10
CONV8
CONV8
t
I
I
V
V
REC
REF
REF
RH
RL
-V
MC9S12DP256B Device User Guide — V02.14
RL
V
V
4.50
DDA
Min
0.5
14
12
SSA
7
6
/2
5.00
Typ
V
0.750
0.375
V
Max
5.25
DDA
2.0
28
14
26
13
20
DDA
/2
Cycles
Cycles
MHz
Unit
mA
mA
V
V
V
s
s
s
97
S