ST72521 datasheet(194/211 Pages) STMICROELECTRONICS

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ST72521

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10-BIT ADC CHARACTERISTICS (Cont’d)

12.12.3 ADC Accuracy

Conditions: VDD=5V

Notes:

1. Injecting negative current on any of the analog input pins significantly reduces the accuracy of any conversion being

performed on any analog input.

Analog pins can be protected against negative injection by adding a Schottky diode (pin to ground). Injecting negative

current on digital input pins degrades ADC accuracy especially if performed on a pin close to the analog input pins.

Any positive injection current within the limits specified for IINJ(PIN) and ΣIINJ(PIN) in Section 12.8 does not affect the ADC

accuracy.

2. Data based on characterization results, monitored in production.

Figure 118. ADC Accuracy Characteristics

Symbol

Parameter

Conditions

Typ

Max

Unit

|ET|

Total unadjusted error1)

LSB

Offset error 1)

3.52)

Gain Error 1)

-0.5

-22)

|ED|

Differential linearity error 1)

CPU in run mode @ fADC 2 MHz.

1.5

4.52)

|EL|

Integral linearity error 1)

CPU in run mode @ fADC 2 MHz.

1.5

4.52)

1LSBIDEAL

1LSB

IDEAL

AREF

SS A

–

1024

--------------------------------------------

Vin (LSBIDEAL)

(1) Example of an actual transfer curve

(2) The ideal transfer curve

(3) End point correlation line

ET=Total Unadjusted Error: maximum deviation

between the actual and the ideal transfer curves.

EO=Offset Error: deviation between the first actual

transition and the first ideal one.

EG=Gain Error: deviation between the last ideal

transition and the last actual one.

ED=Differential Linearity Error: maximum deviation

between actual steps and the ideal one.

EL=Integral Linearity Error: maximum deviation

between any actual transition and the end point

correlation line.

Digital Result ADCDR

1023

1022

1021

1234

567

1021 1022 1023 1024

(1)

(2)

(3)

VAREF

VSSA

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