8XC51 datasheet(21/22 Pages) INTEL

21 / 22 page

8XC51GB

AD Glossary of Terms

Absolute Error

The maximum difference between

corresponding actual and ideal code transitions Ab-

solute Error accounts for all deviations of an actual

converter from an ideal converter

Actual Characteristic

The characteristic of an ac-

tual converter The characteristic of a given convert-

er may vary over temperature supply voltage and

frequency conditions An actual characteristic rarely

has ideal first and last transition locations or ideal

code widths It may even vary over multiple conver-

sions under the same conditions

Break-Before-Make

The property of a multiplexer

which guarantees that a previously selected channel

will be deselected before a new channel is selected

(eg the converter will not short inputs together)

Channel-to-Channel Matching

The difference be-

tween corresponding code transitions of actual char-

acteristics taken from different channels under the

same temperature voltage and frequency condi-

tions

Characteristic

A graph of input voltage versus the

resultant output code for an AD converter It de-

scribes the transfer function of the AD converter

Code

The digital value output by the converter

Code Center

The voltage corresponding to the

midpoint between two adjacent code transitions

Code Transition

The point at which the converter

changes from an output code of Q to a code of Q a

1 The input voltage corresponding to a code tran-

sition is defined to be that voltage which is equally

likely to produce either of two adjacent codes

Code Width

The voltage corresponding to the dif-

ference between two adjacent code transitions

Crosstalk

See ‘‘Off-Isolation’’

DC Input Leakage

Leakage current to ground

from an analog input pin

Differential

Non-Linearity

The difference be-

tween the ideal and actual code widths of the termi-

nal based characteristic

Feedthrough

Attenuation of a voltage applied on

the selected channel of the AD Converter after the

sample window closes

Full Scale Error

The difference between the ex-

pected and actual input voltage corresponding to

the full scale code transition

Ideal Characteristic

A characteristic with its first

code transition at VIN e 05 LSB its last code tran-

sition at VIN e (VREF b 15 LSB) and all code

widths equal to one LSB

Input Resistance

The effective series resistance

from the analog input pin to the sample capacitor

LSBLeast Significant Bit

The voltage corre-

sponding to the full scale voltage divided by 2n

where n is the number of bits of resolution of the

converter For an 8-bit converter with a reference

voltage of 512V one LSB is 20 mV Note that this is

different than digital LSBs since an uncertainty of

two LSBs when referring to an AD converter

equals 40 mV (This has been confused with an un-

certainty of two digital bits which would mean four

counts or 80 mV)

Monotonic

The property of successive approxi-

mation converters which guarantees that increasing

input voltages produce adjacent codes of increasing

value and that decreasing input voltages produce

adjacent codes of decreasing value

No Missed Codes

For each and every output

code there exists a unique input voltage range

which produces that code only

Non-Linearity

The maximum deviation of code

transitions of the terminal based characteristic from

the corresponding code transitions of the ideal char-

acteristic

Off-Isolation

Attenuation of a voltage applied on a

deselected channel of the AD converter (Also re-

ferred to as Crosstalk)

Repeatability

The

difference

between

corre-

sponding code transitions from different actual char-

acteristics taken from the same converter on the

same channel at the same temperature voltage and

frequency conditions

Resolution

The number of input voltage levels

that the converter can unambiguously distinguish

between Also defines the number of useful bits of

information which the converter can return

Sample Delay

The delay from receiving the start

conversion signal to when the sample window

opens

Sample Delay Uncertainty

The variation in the

sample delay

Sample Time

The time that the sample window is

open

Sample Time Uncertainty

The variation in the

sample time

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