STR71XF datasheet(67/78 Pages) STMICROELECTRONICS

67 / 78 page

STR71xF

Electrical parameters

67/78

Data based on characterisation, not tested in production.

ADC Accuracy vs. Negative Injection Current: Injecting negative current on any of the standard (non-

robust) analog input pins should be avoided as this significantly reduces the accuracy of the conversion

being performed on another analog input. It is recommended to add a Schottky diode (pin to ground) to

standard analog pins which may potentially inject negative current. The effect of negative injection current

on robust pins is specified in Section 4.3.5.

Any positive injection current within the limits specified for IINJ(PIN) and ΣIINJ(PIN) in Section 4.3.5 does not

affect the ADC accuracy.

Figure 38.

ADC accuracy characteristics

Table 43.

ADC accuracy with fPCLK2 = 20 MHz, fADC=10 MHz, AVDD=3.3 V

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

ADC_DATA(0V)

Converted code when AIN=0V 1)

2370

2565

Dec-

imal

code

ADC_DATA(2.5V) Converted code when AIN=2.5V 1)

1480

1680

VCM

Center voltage of Sigma-Delta

Modulator1)

1.23

1.25

1.30

TUE

Total unadjusted error

In this type of ADC, calibration is necessary to correct

gain error and offset errors. Once calibrated, the TUE is

limited to the ILE.

|ED|

Differential linearity error1)

1.96

2.19

LSB

|EL|

Integral linearity error 1)

2.36

3.95

1LSBIDEAL

1LSB

IDEAL

AVDD

AVSS

–

4095

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

VAIN (LSBIDEAL)

(1) Example of an actual transfer curve

(2) The ideal transfer curve

(3) End point correlation line

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.

4095

4094

4093

123

4093 4094 4095

(1)

(2)

(3)

AVDD

AVSS

ADC_DATA(0V)

ADC_DATA(2.5V)

VCM

3100 3101 3102 3103

Out of range

1633

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