900844 datasheet(90/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

ADC SUBSYSTEM

Some of the internal signals are first scaled to adapt the range to the input range of the ADC. Note that the 10 bit ADC core

will convert over the entire scaled version of the input channel, so always from a 2.40 V, full scale.

For some applications, an external resistor divider network may be used to scale down the voltage to be measured to the ADC

input range. The source resistance presented by this may be greater than the maximum specified Rs, see ADC Section on

Table 3. In that case, the readout value will be lower than expected due to the dynamic input impedance of the ADC converter.

This readout error presents itself as a gain error which can be compensated for by factory phasing. An alternative is to place a

100 nF bypass capacitor at the ADIN input concerned.

RESERVED CHANNELS POSSIBLE USAGE

Only 22 of the possible 32 ADC channels are currently associated with an specific function. The remaining channels are

currently designated as reserved channels for future needs. Table 58 is a proposed usage for some of these channels for

additional flexibility.

01000

Reserved

01001

Battery Pack Thermistor

0 – 2.4 V

0– 2.4 V

01010

General Purpose ADIN10

Touch screen X+

0-200 mV / 0-2.0 V

0 – 1.2

10x / 1x

0 – 2.4 V

01011

General Purpose ADIN11

Touch screen X-

0-200 mV / 0-2.0 V

0 – 1.2

10x / 1x

0 – 2.4 V

01100

General Purpose ADIN12

Touch screen Y+

0-200 mV / 0-2.0 V

0 – 1.2

10x / 1x

0 – 2.4 V

01101

General Purpose ADIN13

Touch screen Y-

0-200 mV / 0-2.0 V

0 – 1.2

10x / 1x

0 – 2.4 V

01110

General Purpose ADIN14

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

01111

General Purpose ADIN15

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10000

General Purpose ADIN16

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10001

General Purpose ADIN17

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10010

General Purpose ADIN18

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10011

General Purpose ADIN19

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10100

General Purpose ADIN20

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10101

General Purpose ADIN21

0-200 mV / 0-2.0 V

10x / 1x

0 – 2.4 V

10110

Reserved

10111

Reserved

11000

Reserved

11001

Reserved

11010

Reserved

11011

Reserved

11100

Reserved

11101

Reserved

11110

Reserved

11111

Reserved

Notes

18.

Equivalent to -3.0 to +3.0 A of current with a 20 mOhm sense resistor

Table 57. ADC Inputs

Channel

SELECT[4:0]

ADC Input Signal

Input Level

Scaling

Scaled Version

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