MC9S12XD256MAL Datasheet, PDF (1252/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Appendix A Electrical Characteristics
Table A-13. ATD Operating Characteristics 3.3V
Conditions are shown in Table A-4 unless otherwise noted, Supply Voltage 3.15V < VDDA < 3.6V
Num C
Rating
Symbol
Min
Typ
Max
Unit
1 D Reference potential
Low
High
2 C Differential reference voltage¹
V_RL
V_SSA
—
V_DDA/2
V
V_RH
V_DDA/2
—
V_DDA
V
V_RH-V_RL
3.15
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 cycles²
Conv, time at 2.0 MHz ATD clock f_ATDCLK
N_CONV10
14
—
28
Cycles
T_CONV10
7
—
14
µs
5 D ATD 8-bit conversion period
Clock cycles²
Conv, time at 2.0 MHz ATD clock f_ATDCLK
N_CONV8
12
—
26
Cycles
T_CONV8
6
—
13
µs
6 D Recovery time (V_DDA = 5.0 Volts)
t_REC
—
—
20
µs
7 P Reference supply current 2 ATD blocks on
I_REF
—
—
0.500
mA
8 P Reference supply current 1 ATD block on
I_REF
—
—
0.250
mA
1 _{Full accuracy is not guaranteed when differential voltage is less than 3.15 V}
2 _{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.2.2 Factors Influencing Accuracy
Three factors — source resistance, source capacitance and current injection — have an influence on the
accuracy of the ATD.
A.2.2.1 Source Resistance
Due to the input pin leakage current as specified in 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 (2.5 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 is allowed.
A.2.2.2 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).
1254
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor