PC912XDP512F0MPVR datasheet(1252/1348 Pages) FREESCALE

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Appendix A Electrical Characteristics

MC9S12XDP512 Data Sheet, Rev. 2.21

1254

Freescale Semiconductor

Table A-13. ATD Operating Characteristics 3.3V

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 RS

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, Cf ≥ 1024 * (CINS–CINN).

Conditions are shown in Table A-4 unless otherwise noted, Supply Voltage 3.15V < VDDA < 3.6V

Num

Rating

Symbol

Min

Typ

Max

Unit

D Reference potential

Low

High

VRL

VRH

VSSA

VDDA/2

—

VDDA/2

VDDA

C Differential reference voltage1

1 Full accuracy is not guaranteed when differential voltage is less than 3.15 V

VRH-VRL

3.15

3.3

3.6

D ATD clock frequency

fATDCLK

0.5

—

2.0

MHz

D ATD 10-bit conversion period

Clock cycles2

Conv, time at 2.0 MHz ATD clock fATDCLK

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.

NCONV10

TCONV10

—

Cycles

µs

D ATD 8-bit conversion period

Clock cycles2

Conv, time at 2.0 MHz ATD clock fATDCLK

NCONV8

TCONV8

—

Cycles

µs

D Recovery time (VDDA = 5.0 Volts)

tREC

——

µs

P Reference supply current 2 ATD blocks on

IREF

—

0.500

P Reference supply current 1 ATD block on

IREF

—

0.250

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