AN2834 datasheet(28/45 Pages) STMICROELECTRONICS

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How to get the best ADC accuracy

AN2834

28/45

DocID15067 Rev 2

3.2.8

Temperature-effect compensation

One method would be to fully characterize the offset and gain drift and provide a lookup

table in memory to correct measurement according to temperature change. This calibration

involves additional cost and takes time.

The second method consists in recalibrating the ADC when the temperature change

reaches given values, by using the internal temperature sensor and the ADC watchdog.

3.2.9

Minimizing injection current

Check the application to verify whether any digital or analog input voltage can be less than

VSS or VSSA. If it is the case, a negative injection current will flow from the pins. The effect

on the accuracy will be greater if a digital input is close to the analog input being converted.

Negative current injection on any of the standard (non-robust) analog input pins should be

avoided as this would significantly reduce the accuracy of the conversion being performed

on another analog input.

It is recommended to connect a Schottky diode between VSSA and the I/O pin that can give

birth to the negative injection current.

The ADC accuracy will not be affected by positive injection currents within the limits

specified for IINJ(PIN) and ΣIINJ(PIN) (refer to the appropriate STM32x datasheet, I/O port

characteristics section).

3.2.10

Minimizing I/O pin crosstalk

The noise produced by crosstalk can be reduced by shielding the analog signal by placing

ground tracks across it. Figure 27 shows the recommended grounding between signals.

Figure 27. Crosstalk between I/O pins

Analog

Digital

I/O

STM32

ai15490

AN2834 Datasheet(PDF) 28 Page - STMicroelectronics