AN2834 datasheet(14/45 Pages) STMICROELECTRONICS

Part #	AN2834

Description	How to get the best ADC accuracy in STM32Fx Series and STM32L1 Series devices

PDF	45 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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14 / 45 page

ADC errors

AN2834

14/45

DocID15067 Rev 2

2.1.5

Total unadjusted error

The total unadjusted error (TUE) is defined as the maximum deviation between the actual

and the ideal transfer curves. It is a parameter that specifies the total errors that may occur,

causing maximum deviation between the ideal digital output and the actual digital output. It

is the maximum deviation recorded between the ideal expected value and the actual value

obtained from the ADC for any input voltage.

The TUE is denoted by ET. It is represented in Figure 13.

The TUE is not the sum of EO, EG, EL, ED. The offset error affects the digital result at lower

voltages whereas the gain error affects the digital output for higher voltages.

Example

If VREF+ = 3.3 V and VAIN = 2 V, the ideal result is 9B2h. But if, on conversion, we get the

result 9B4h, the deviation may result from the offset since the DLE and ILE errors occur

simultaneously.

TUE = absolute (actual value – ideal case value) = 9B4h – 9B2h = 2h = 2LSB

Figure 13. Total unadjusted error

VAIN

Digital output

ai15481

Ideal transfer curve

Actual transfer curve

AN2834 Datasheet(PDF) 14 Page - STMicroelectronics