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MC9S12E128 Datasheet, PDF (590/606 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers | |||
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Appendix A Electrical Characteristics
A.6.2 ATD Operating Characteristics â 3.3V Range
The Table A-20 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 A-20. 3.3V ATD Operating Characteristics
Conditions are shown in Table A-4 unless otherwise noted; Supply Voltage 3.3V-10% <= VDDA <= 3.3V+10%
Num C
Rating
Symbol
Min
Typ
Max
Unit
1 D Reference Potential
Low
VRL
VSSA
â
VDDA/2
V
High VRH
VDDA/2
â
VDDA
V
2 C Differential Reference Voltage
VRH-VRL
3.0
3.3
3.6
V
3 D ATD Clock Frequency
fATDCLK
0.5
â
2.0
MHz
4 D ATD 10-Bit Conversion Period
Clock Cycles1 NCONV10
14
â
28
Cycles
Conv, Time at 2.0MHz ATD Clock fATDCLK TCONV10
7
â
14
µs
Conv, Time at 4.0MHz2 ATD Clock fATDCLK TCONV10
3.5
â
7
µs
5 D ATD 8-Bit Conversion Period
Clock Cycles1 NCONV8
12
â
26
Cycles
Conv, Time at 2.0MHz ATD Clock fATDCLK TCONV8
6
â
13
µs
6 D Recovery Time (VDDA=3.3 Volts)
tREC
â
â
20
µs
7 P Reference Supply current
IREF
â
â
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.
2 Reduced accuracy see Table A-22 and Table A-23.
A.6.3 Factors Inï¬uencing Accuracy
Three factors â source resistance, source capacitance and current injection â have an inï¬uence on the
accuracy of the ATD.
A.6.3.1 Source Resistance
Due to the input pin leakage current as speciï¬ed in Table A-6 and Table A-7 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 (2.5mV) 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 are allowed.
MC9S12E128 Data Sheet, Rev. 1.07
590
Freescale Semiconductor
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