ST10F273E datasheet(137/179 Pages) STMICROELECTRONICS

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ST10F273E

Electrical characteristics

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24.7.2

A/D conversion accuracy

The A/D Converter compares the analog voltage sampled on the selected analog input

channel to its analog reference voltage (VAREF) and converts it into 10-bit digital data. The

absolute accuracy of the A/D conversion is the deviation between the input analog value and

the output digital value. It includes the following errors:

●

Offset error (OFS)

●

Gain Error (GE)

●

Quantization error

●

Non-Linearity error (Differential and Integral)

These four error quantities are explained below using

Figure 37.

Offset error

Offset error is the deviation between actual and ideal A/D conversion characteristics when

the digital output value changes from the minimum (zero voltage) 00 to 01 (

Figure 37, see

OFS).

Gain error

Gain error is the deviation between the actual and ideal A/D conversion characteristics when

the digital output value changes from the 3FE to the maximum 3FF, once offset error is

subtracted. Gain error combined with offset error represents the so-called full-scale error

(

Figure 37, OFS + GE).

Quantization error

Quantization error is the intrinsic error of the A/D converter and is expressed as 1/2 LSB.

Non-linearity error

Non-Linearity error is the deviation between actual and the best-fitting A/D conversion

characteristics (see

Figure 37):

●

Differential Non-Linearity error is the actual step dimension versus the ideal one (1

LSBIDEAL).

●

Integral Non-Linearity error is the distance between the center of the actual step and

the center of the bisector line, in the actual characteristics. Note that for Integral Non-

Linearity error, the effect of offset, gain and quantization errors is not included.

Note:

Bisector characteristic is obtained drawing a line from 1/2 LSB before the first step of the

real characteristic, and 1/2 LSB after the last step again of the real characteristic.

24.7.3

Total unadjusted error

The Total Unadjusted Error specifies the maximum deviation from the ideal characteristic:

the number provided in the Data Sheet represents the maximum error with respect to the

entire characteristic. It is a combination of the Offset, Gain and Integral Linearity errors. The

different errors may compensate each other depending on the relative sign of the Offset and

Gain errors. Refer to

Figure 37, see TUE.

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