MC9S12NE64_06 Datasheet, PDF (512/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

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 — 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:
V_SSA ≤ V_RL ≤ V_IN ≤ V_RH ≤ V_DDA. 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 18-27. 3.3V ATD Operating Characteristics
Conditions are shown in Table A-4 unless otherwise noted; Supply Voltage 3.3 V-10% <= V_DDA <= 3.3 V +10%
Num C
Rating
Symbol Min
Typ
Max
Unit
1 D Reference Potential
Low
V_RL
High V_RH
V_SSA
V_DDA/2
V_DDA/2
V
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
4 D ATD 10-Bit Conversion Period
Clock Cycles ^{1 N}CONV10
14
Conv, Time at 2.0 MHz ATD Clock f_ATDCLK ^TCONV10
7
2.0
MHz
28
Cycles
14
µs
5 D ATD 8-Bit Conversion Period
Clock Cycles^{1 N}CONV8
12
Conv, Time at 2.0 MHz ATD Clock f_ATDCLK ^TCONV8
6
26
Cycles
13
µs
6 D Recovery Time (V_DDA = 3.3 V)
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.
A.11.2 Factors Influencing Accuracy
Three factors — source resistance, source capacitance, and current injection — have an influence on the
accuracy of the ATD.
A.11.2.1 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_S
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 are allowed.
MC9S12NE64 Data Sheet, Rev. 1.1
512
Freescale Semiconductor