MC9S12E64CFUE Datasheet, PDF (590/606 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
A.6.2 ATD Operating Characteristics — 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 amplifier 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% <= V_DDA <= 3.3V+10%
Num C
Rating
Symbol
Min
Typ
Max
Unit
1 D Reference Potential
Low
V_RL
V_SSA
—
V_DDA/2
V
High V_RH
V_DDA/2
—
V_DDA
V
2 C Differential Reference Voltage
V_RH-V_RL
3.0
3.3
3.6
V
3 D ATD Clock Frequency
f_ATDCLK
0.5
—
2.0
MHz
4 D ATD 10-Bit Conversion Period
Clock Cycles¹ N_CONV10
14
—
28
Cycles
Conv, Time at 2.0MHz ATD Clock f_ATDCLK T_CONV10
7
—
14
µs
Conv, Time at 4.0MHz² ATD Clock f_ATDCLK T_CONV10
3.5
—
7
µs
5 D ATD 8-Bit Conversion Period
Clock Cycles¹ N_CONV8
12
—
26
Cycles
Conv, Time at 2.0MHz ATD Clock f_ATDCLK T_CONV8
6
—
13
µs
6 D Recovery Time (V_DDA=3.3 Volts)
t_REC
—
—
20
µs
7 P Reference Supply current
I_REF
—
—
0.250
mA
1 _{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.
2 _{Reduced accuracy see Table A-22 and Table A-23.}
A.6.3 Factors Influencing Accuracy
Three factors — source resistance, source capacitance and current injection — have an influence on the
accuracy of the ATD.
A.6.3.1 Source Resistance
Due to the input pin leakage current as specified 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 R_S specifies 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