SPMCK16Z4MPV16 datasheet(201/500 Pages) FREESCALE

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M68HC16 Z SERIES

ANALOG-TO-DIGITAL CONVERTER

USER’S MANUAL

8-15

Figure 8-4 Analog Input Circuitry

Since the sample amplifier is powered by VDDA and VSSA, it can accurately transfer

input signal levels up to but not exceeding VDDA and down to but not below VSSA.If

the input signal is outside of this range, the output from the sample amplifier is clipped.

In addition, VRH and VRL must be within the range defined by VDDA and VSSA. As long

as VRH is less than or equal to VDDA, and VRL is greater than or equal to VSSA, and

the sample amplifier has accurately transferred the input signal, resolution is ratiomet-

ric within the limits defined by VRL and VRH.IfVRH is greater than VDDA, the sample

amplifier can never transfer a full-scale value. If VRL is less than VSSA, the sample am-

plifier can never transfer a zero value.

Figure 8-5 shows the results of reference voltages outside the range defined by VDDA

and VSSA. At the top of the input signal range, VDDA is 10 mV lower than VRH. This

results in a maximum obtainable 10-bit conversion value of 3FE. At the bottom of the

signal range, VSSA is 15 mV higher than VRL, resulting in a minimum obtainable 10-bit

conversion value of three.

SAMPLE

AMP

8 CHANNELS TOTAL1

RC DAC

ARRAY

COMPARATOR

REF 1

VSSA

VRL

REF 2

VDDA

VRH

ADC 8CH SAMPLE AMP

1. TWO SAMPLE AMPS EXIST ON THE ADC WITH EIGHT CHANNELS ON EACH SAMPLE AMP.

NOTES:

Freescale Semiconductor, Inc.

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