Datasheet

DocID14611 Rev 10 105/136
STM32F103xC, STM32F103xD, STM32F103xE Electrical characteristics
129
Equation 1: R
AIN
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 60.R
AIN
max for f
ADC
= 14 MHz
(1)
1. Guaranteed by design, not tested in production.
T
s
(cycles) t
S
(µs) R
AIN
max (kΩ)
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 50
71.5 5.11 NA
239.5 17.1 NA
Table 61.ADC accuracy - limited test conditions
(1)(2)
1. ADC DC accuracy values are measured after internal calibration.
2. ADC Accuracy vs. Negative Injection Current: Injecting 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 which may potentially
inject negative current.
Any positive injection current within the limits specified for I
INJ(PIN)
and ΣI
INJ(PIN)
in Section 5.3.14 does not
affect the ADC accuracy.
Symbol Parameter Test conditions Typ Max
(3)
3. Based on characterisation, not tested in production.
Unit
ET Total unadjusted error f
PCLK2
= 56 MHz,
f
ADC
= 14 MHz, R
AIN
< 10 kΩ,
V
DDA
= 3 V to 3.6 V
T
A
= 25 °C
Measurements made after
ADC calibration
V
REF+
= V
DDA
±1.3 ±2
LSB
EO Offset error ±1 ±1.5
EG Gain error ±0.5 ±1.5
ED Differential linearity error ±0.7 ±1
EL Integral linearity error ±0.8 ±1.5
R
AIN
T
S
f
ADC
C
ADC
2
N2+
()ln××
--------------------------------------------------------------- - R
ADC
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