SPC560P50L3 datasheet(79/112 Pages) STMICROELECTRONICS

79 / 112 page

SPC560P44Lx, SPC560P50Lx

Electrical characteristics

Doc ID 14723 Rev 9

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Figure 15.

ADC characteristics and error definitions

3.14.1

Input impedance and ADC accuracy

To preserve the accuracy of the A/D converter, it is necessary that analog input pins have

low AC impedance. Placing a capacitor with good high frequency characteristics at the input

pin of the device can be effective: the capacitor should be as large as possible, ideally

infinite. This capacitor contributes to attenuating the noise present on the input pin; further, it

sources charge during the sampling phase, when the analog signal source is a high-

impedance source.

A real filter can typically be obtained by using a series resistance with a capacitor on the

input pin (simple RC filter). The RC filtering may be limited according to the source

impedance value of the transducer or circuit supplying the analog signal to be measured.

(2)

(1)

(3)

(4)

(5)

Offset Error OSE

Gain Error GE

1 LSB (ideal)

1023

1022

1021

1020

1019

1018

1017 1018 1019 1020 1021 1022 1023

(1) Example of an actual transfer curve

(2) The ideal transfer curve

(3) Differential non-linearity error (DNL)

(4) Integral non-linearity error (INL)

(5) Center of a step of the actual transfer curve

1 LSB ideal = VDD_ADC / 1024

Vin(A) (LSBideal)

code out

SPC560P50L3 Datasheet(PDF) 79 Page - STMicroelectronics