STRT71XF datasheet(64/74 Pages) STMICROELECTRONICS

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Electrical parameters

STR71xF

64/74

Figure 34. ADC Accuracy Characteristics

Analog Power Supply and Reference Pins

The AVDD and AVSS pins are the analog power supply of the A/D converter cell. They act as

the high and low reference voltages for the conversion.

Separation of the digital and analog power pins allow board designers to improve A/D

performance. Conversion accuracy can be impacted by voltage drops and noise in the event

of heavily loaded or badly decoupled power supply lines (see: General PCB Design

Guidelines).

General PCB Design Guidelines

To obtain best results, some general design and layout rules should be followed when

designing the application PCB to shield the noise-sensitive, analog physical interface from

noise-generating CMOS logic signals.

●

Use separate digital and analog planes. The analog ground plane should be connected

to the digital ground plane via a single point on the PCB.

●

Filter power to the analog power planes. It is recommended to connect capacitors, with

good high frequency characteristics, between the power and ground lines, placing

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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