Electrical characteristics
Equation 1: R
STM32F103xC, STM32F103xD, STM32F103xE
max formula
AIN
TS
RAIN < ------------------------------------------------------------- – RADC
fADC × CADC × ln(2N + 2
)
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).
(1)
Table 60.
R
max for f
= 14 MHz
AIN
ADC
Ts (cycles)
tS (µs)
RAIN max (kΩ)
1.5
0.11
0.4
7.5
0.54
0.96
2.04
2.96
3.96
5.11
17.1
5.9
13.5
28.5
41.5
55.5
71.5
239.5
11.4
25.2
37.2
50
NA
NA
1. Guaranteed by design, not tested in production.
(1)(2)
Table 61. ADC accuracy - limited test conditions
Symbol
Parameter
Test conditions
Typ
Max(3)
Unit
ET
EO
EG
ED
Total unadjusted error
Offset error
fPCLK2 = 56 MHz,
1.3
1
2
1.5
1.5
1
fADC = 14 MHz, RAIN < 10 kΩ,
VDDA = 3 V to 3.6 V
TA = 25 °C
Gain error
0.5
0.7
LSB
Measurements made after
ADC calibration
VREF+ = VDDA
Differential linearity error
EL
Integral linearity error
0.8
1.5
1. ADC DC accuracy values are measured after internal calibration.
2. ADC Accuracy vs. Negative Injection Current: Injecting negative current on any of the standard (non-
robust) 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
standard analog pins which may potentially inject negative current.
Any positive injection current within the limits specified for IINJ(PIN) and ΣIINJ(PIN) in Section 5.3.14 does not
affect the ADC accuracy.
3. Based on characterisation, not tested in production.
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Doc ID 14611 Rev 8
STMICROELECTRONICS [ ST ]
