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MC9S12NE64V1 Datasheet, PDF (512/554 Pages) Freescale Semiconductor, Inc – MC9S12NE64V1 Data Sheet | |||
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Appendix A Electrical Characteristics
A.11 ATD Electrical Characteristics
This section describes the characteristics of the analog-to-digital converter.
A.11.1 ATD Operating Characteristics â 3.3 V Range
Table 18-27 shows conditions under which the ATD operates.
The following constraints exist to obtain full-scale, full range results:
VSSA ⤠VRL ⤠VIN ⤠VRH ⤠VDDA. This constraint exists since the sample buffer ampliï¬er can not drive
beyond the power supply levels that it ties to. If the input level goes outside of this range it will effectively
be clipped.
Table 18-27. 3.3V ATD Operating Characteristics
Conditions are shown in Table A-4 unless otherwise noted; Supply Voltage 3.3 V-10% <= VDDA <= 3.3 V +10%
Num C
Rating
Symbol Min
Typ
Max
Unit
1 D Reference Potential
Low
VRL
High VRH
VSSA
VDDA/2
VDDA/2
V
VDDA
V
2 C Differential Reference Voltage
VRH-VRL
3.0
3.3
3.6
V
3 D ATD Clock Frequency
fATDCLK
0.5
4 D ATD 10-Bit Conversion Period
Clock Cycles 1 NCONV10
14
Conv, Time at 2.0 MHz ATD Clock fATDCLK TCONV10
7
2.0
MHz
28
Cycles
14
µs
5 D ATD 8-Bit Conversion Period
Clock Cycles1 NCONV8
12
Conv, Time at 2.0 MHz ATD Clock fATDCLK TCONV8
6
26
Cycles
13
µs
6 D Recovery Time (VDDA = 3.3 V)
tREC
20
µs
7 P Reference Supply current
IREF
0.250
mA
1 The minimum time assumes a ï¬nal sample period of 2 ATD clocks cycles while the maximum time assumes a ï¬nal sample
period of 16 ATD clocks.
A.11.2 Factors Influencing Accuracy
Three factors â source resistance, source capacitance, and current injection â have an inï¬uence on the
accuracy of the ATD.
A.11.2.1 Source Resistance
Due to the input pin leakage current as speciï¬ed 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 RS
speciï¬es 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 are allowed.
MC9S12NE64 Data Sheet, Rev. 1.1
512
Freescale Semiconductor
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