AN2021 datasheet(14/39 Pages) STMICROELECTRONICS

14 / 39 page

Modified features

AN2021

14/39

Note:

The VAREF pin is also used as a supply pin for the ADC module. As there is a higher current

sink on this pin on the ST10F272 compared to the ST10F269, it is recommended not to

connect a resistor (for example, because of an RC filter), to prevent creating an offset in the

reference.

1.4.3

Software impact

Self-calibration and ADC initialization routine

An automatic self-calibration adjusts the ADC module to process parameter variations at

each reset event. After reset, the busy flag (read-only) ADBSY is set because the self-

calibration is ongoing. The duration of self-calibration depends on the CPU clock: It may

take up to 40.629 ± 1 clock pulses. The user must poll this bit to know when self-calibration

is complete in order to initialize the ADC module.

This self-calibration is seen by the ST10F272 as a conversion and thus bit ADCIR is set.

The software should perform a dummy read of the ADDAT register and clear the ADCIR and

ADCEIR flags before configuring the ADC module and starting the first conversion.

New bit ADOFF, bit 6 of ADCON register

The bit 6 of the ADCON register, reserved in previous ST10 devices, is now used to enable

and disable the ADC. By default this bit is cleared and the ST10F272 is compatible with the

ST10F269. Therefore, there is no impact on the software, provided that this bit is not written

to.

IAREF

Reference supply

current

Running mode

Power-down mode

500

5000

µA

DNL

Differential nonlinearity

-0.5

+0.5

-1

LSB

INL

Integral nonlinearity

-1.5

+1.5

-1.5

+1.5

LSB

OFS

Offset error

-1.0

+1.0

-1.5

+1.5

LSB

Table 6.

ADC differences (continued)

Symbol

Parameter

Limit values for ST10F269

Limit values for ST10F272

Unit

Min

Max

Min

Max

ADCON (FFA0h / A0h)

SFR

Reset value: 0000h

765

4321

ADCTC

ADSTC

CRQ

CIN

BSY

OFF

ADM

ADCH

R/W

Table 7.

ADCON register description

Bit

Function

Comment

ADOFF

ADC Disable

0: Analog circuitry of A/D converter is on

1: Analog circuitry of A/D converter is turned off

New bit valid only for the ST10F272.

Reserved on ST10F269.

AN2021 データシート(PDF) 14 Page - STMicroelectronics

AN2021 データシート(HTML) 14 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

データシートダウンロード

リンク URL

AN2021 データシート(PDF) 14 Page - STMicroelectronics

AN2021 データシート(HTML) 14 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

データシート ダウンロード

リンク URL

データシートダウンロード