How To Get The Best Adc Accuracy; Reduce The Effects Of Adc-Related Adc Errors; Minimize Adc Errors Related To External Environment Of Adc; Reference Voltage / Power Supply Noise Minimization - ST STM32 Application Note

How to get the best ADC accuracy

3 How to get the best ADC accuracy
3.1

Reduce the effects of ADC-related ADC errors

The TUE is not the sum of all the E
occur between the ideal and actual digital values. It can result from one or more errors
occurring simultaneously.
As the ILE is the integral of the DLE, it can be considered as the indicator of the maximum
error. Do not add the DLE and ILE together to calculate the maximum error that may occur
at any digital step.
The maximum error values specified in the datasheet are the worst error values measured
in laboratory test environment over the given voltage and temperature range (see device
datasheet).
The ILE and DLE are dependent on the ADC design. It is difficult to calibrate them. They
can be calibrated by the measured ADC curve stored in the microcontroller memory but this
needs calibration of each individual device in final application.
Offset and gain errors can be easily compensated using the STM32 ADC self-calibration
feature or by microcontroller firmware.
3.2

Minimize ADC errors related to external environment of ADC

3.2.1

Reference voltage / Power supply noise minimization

Power supply side
Linear regulators have a better output in terms of noise. The mains must be stepped down,
rectified and filtered, then fed to linear regulators. It is highly recommended to connect the
filter capacitors to the rectifier output. Please refer to the datasheet of the used linear
regulator.
If you are using a switching power supply, it is recommended to have a linear regulator to
supply the analog stage.
It is recommended to connect capacitors with good high-frequency characteristics between
the power and ground lines. That is, a 0.1 µF and a 1 to 10 µF capacitor should be placed
close to the power source.
The capacitors allow the AC signals to pass through them. The small-value capacitors filter
high-frequency noise and the high-value capacitors filter low-frequency noise. Ceramic
capacitors are generally available in small values (1 pF to 0.1 µF) and with small voltage
ratings (16 V to 50 V). It is recommended to place them close to the main supply (V
V ) and analog supply (V
SS
tracks. Small capacitors can react fast to current surges and discharge quickly for fast-
current requirements.
Tantalum capacitors can also be used along with ceramic capacitors. To filter low-frequency
noise, you can use high-value capacitors (10 µF to 100 µF), which are generally electrolytic.
It is recommended to put them near the power source.
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and V ) pins. They filter the noise induced in the PCB
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