S912XHZ512F1VAG Datasheet, PDF (903/978 Pages) Freescale Semiconductor, Inc – Covers MC9S12XHZ384, MC9S12XHZ256

Appendix A Electrical Characteristics
A.2 ATD
This section describes the characteristics of the analog-to-digital converter.
A.2.1 ATD Operating Characteristics
The Table A-11 and Table A-13 show 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 A-11. ATD Operating Characteristics
Conditions are shown in Table A-4 unless otherwise noted, supply voltage 4.5 V < V_DDA < 5.5 V
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
4.50
5.00
5.5
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
I_REF
—
—
0.375
mA
1 _{Full accuracy is not guaranteed when differential voltage is less than 4.50 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-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 is allowed.
MC9S12XHZ512 Data Sheet, Rev. 1.06
Freescale Semiconductor
903