STM32F103CB datasheet(75/116 Pages) STMICROELECTRONICS

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RAIN

fADC CADC





-------------------------------------------------------------- RADC

–



DS5319 Rev 18

75/116

STM32F103x8, STM32F103xB

Electrical characteristics

115

Equation 1: RAIN max formula:

The formula above (Equation 1) is used to determine the maximum external impedance allowed for an

error below 1/4 of LSB. Here N = 12 (from 12-bit resolution).

Table 47. RAIN max for fADC = 14 MHz(1)

1. Evaluated by characterization, not tested in production, unless otherwise specified.

Ts (cycles)

tS (µs)

RAIN max (k)

1.5

0.11

0.4

7.5

0.54

5.9

13.5

0.96

11.4

28.5

2.04

25.2

41.5

2.96

37.2

55.5

3.96

71.5

5.11

239.5

17.1

Table 48. ADC accuracy - Limited test conditions(1) (2)

1. ADC DC accuracy values are measured after internal calibration.

2. Injecting a negative current on any analog input pins should be avoided as this significantly reduces the

accuracy of the conversion being performed on another analog input. It is recommended to add a Schottky

diode (pin to ground) to analog pins that may potentially inject negative currents.



Any positive injection current within the limits specified for IINJ(PIN) and IINJ(PIN) in Section 5.3.12 does not

affect the ADC accuracy.

Symbol

Parameter

Test conditions

Typ

Max(3)

3. Evaluated by characterization, not tested in production, unless otherwise specified.

Unit

Total unadjusted error

fPCLK2 = 56 MHz,

fADC = 14 MHz, RAIN < 10 kΩ,

VDDA = 3 V to 3.6 V, 

TA = 25 °C

Measurements made after

ADC calibration

±1.3

±2

LSB

Offset error

±1.0

±1.5

Gain error

±0.5

±1.5

Differential linearity error

±0.7

±1.0

Integral linearity error

±0.8

±1.5

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