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UNDERSTANDING AND MINIMISING ADC CONVERSION ERRORS

ED= (5.12mV/4.88mV) LSB

ED= 1.04 LSB

Here we assume that any voltage greater than 1.010 V will not result in the digital code equal

to CDh.

When the step width is less than 1LSB, DLE will be negative.

5.4 INTEGRAL LINEARITY ERROR

Integral Linearity Error is maximum deviation between any actual transition and the endpoint

correlation line. ILE is represented as EL.

The endpoint correlation line can be defined as the line on the A/D transfer curve that con-

nects the first actual transition and last actual transition. ILE is the deviation from this line for

each transition. The endpoint correlation line thus corresponds to the actual transfer curve and

has no relation to the ideal transfer curve.

ILE is also known as INL, Integral Non linearity Error. ILE is the integral of DLE over the full

range.

Figure 30. Integral error representation

Example:

If we get the first transition from 0 to 1 at 10mV ( offset error ) and we get the last transition

(3FE to 3FF) at 4.990V (gain error) then the line on transfer curve connecting the actual digital

code 1 and the actual digital code 3FF will be the endpoint correlation line.

VIN

VSSA

Digital

output

(Decimal

steps)

EL = Integral linearity error

transfer curve

Actual

Endpoint correlation

Line

1023

AN1636 Datasheet(PDF) 32 Page - STMicroelectronics