ST7LUS5 datasheet(76/124 Pages) STMICROELECTRONICS

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On-chip peripherals

ST7LUS5, ST7LU05, ST7LU09

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10.3.3

Functional description

Analog power supply

VDDA and VSSA are the high and low level reference voltage pins. In some devices (refer to

device pin out description) they are internally connected to the VDD and VSS pins.

Conversion accuracy may therefore be impacted by voltage drops and noise in the event of

heavily loaded or badly decoupled power supply lines.

Figure 34.

ADC block diagram

Digital A/D conversion result

The conversion is monotonic, meaning that the result never decreases if the analog input

does not and never increases if the analog input does not.

If the input voltage (VAIN) is greater than VDDA (high-level voltage reference) then the

conversion result is FFh in the ADCDRH register and 03h in the ADCDRL register (without

overflow indication).

If the input voltage (VAIN) is lower than VSSA (low-level voltage reference) then the

conversion result in the ADCDRH and ADCDRL registers is 00 00h.

The A/D converter is linear and the digital result of the conversion is stored in the ADCDRH

and ADCDRL registers. The accuracy of the conversion is described in the Chapter 12:

Electrical characteristics.

CH2

CH1

EOC SPEED ADON

CH0

ADCCSR

AIN0

AIN1

ANALOG TO DIGITAL

CONVERTER

AINx

ANALOG

MUX

ADCDRH

ADCDRL

SLOW

RADC

CADC

HOLD CONTROL

fADC

fCPU

DIV 2

DIV 4

SLOW

bit

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