MC9S12KG128 Datasheet, PDF (574/600 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
Table A-12. 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 (two ATD modules)
I_REF
—
—
0.500
mA
8 P Reference Supply current (one ATD module)
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-14 and Table A-15.}
A.5.2 Factors Influencing Accuracy
Three factors — source resistance, source capacitance and current injection — have an influence on the
accuracy of the ATD.
A.5.2.1 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.
A.5.2.2 Source Capacitance
When sampling an additional internal capacitor is switched to the input. This can cause a voltage drop due
to charge sharing with the external and the pin capacitance. For a maximum sampling error of the input
voltage ≤ 1LSB, then the external filter capacitor, C_f ≥ 1024 * (C_INS–C_INN).
MC9S12KG128 Data Sheet, Rev. 1.15
574
Freescale Semiconductor