AN1830 datasheet(3/15 Pages) STMICROELECTRONICS

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ACHIEVING HIGH ACCURACY AND 13-BIT RESOLUTION WITH ST7LITE2 ADC

DATA REGISTER HIGH (ADCDRH)

This read only register provides MSB D[9:2] of the A/D conversion result.

AMP CONTROL/DATA REGISTER LOW (ADCDRL)

The read/write register can be used to:

- Provide LSB D[1:0] of the A/D conversion result.

- Select amplifier functionality: Amplifier select and Calibration (AMPSEL and AMPCAL)

- To configure fADC along with the SPEED bit in the ADCCSR register (SLOW)

For a detailed description of each bit, refer to the ST7LITE2 datasheet.

2.2 UNDERSTANDING THE ADC INTERNAL AMPLIFIER

The purpose of the amplifier is to amplify an input voltage at analog input by a factor of 8. The

amplifier output is fed to the ADC. The amplifier introduces an offset at the output (VOFFSET).

Thus the output becomes:

VOUT(Amplifier) = VOFFSET + 8 x VIN

where,

VOFFSET is the output offset voltage of the amplifier.

VIN is the amplifier input voltage (= AINx). Its range depends on the VDD supply voltage.

The amplifier is switched ON by the ADON bit in the ADCCSR register, so no additional start-

up time is required when the amplifier is selected by the AMPSEL bit.

You can also switch between the direct input and the amplified input i.e. the output of the am-

plifier can be either equal to its input or equal to the amplified output. This is controlled by the

control signal AMPSEL.

AMP

CAL

SLOW

AMP-

SEL

AN1830 Fiches technique(PDF) 3 Page - STMicroelectronics