DocID025832 Rev 2
STM32F042xx
Electrical characteristics
94
The formula above (
) 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 55. R
AIN
max for f
ADC
= 14 MHz
T
s
(cycles)
t
S
(
μ
s)
R
AIN
max (k
)
(1)
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
1. Guaranteed by design, not tested in production.
Table 56. ADC accuracy
(1)(2)(3)
Symbol
Parameter
Test conditions
Typ
Max
(4)
Unit
ET
Total unadjusted error
f
PCLK
= 48 MHz,
f
ADC
= 14 MHz, R
AIN
< 10 k
V
DDA
= 3 V to 3.6 V
T
A
= 25 °C
±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
ET
Total unadjusted error
f
PCLK
= 48 MHz,
f
ADC
= 14 MHz, R
AIN
< 10 k
V
DDA
= 2.7 V to 3.6 V
T
A
=
40 to 105 °C
±3.3
±4
LSB
EO
Offset error
±1.9
±2.8
EG
Gain error
±2.8
±3
ED
Differential linearity error
±0.7
±1.3
EL
Integral linearity error
±1.2
±1.7
ET
Total unadjusted error
f
PCLK
= 48 MHz,
f
ADC
= 14 MHz, R
AIN
< 10 k
V
DDA
= 2.4 V to 3.6 V
T
A
= 25 °C
±3.3
±4
LSB
EO
Offset error
±1.9
±2.8
EG
Gain error
±2.8
±3
ED
Differential linearity error
±0.7
±1.3
EL
Integral linearity error
±1.2
±1.7
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 I
INJ(PIN)
and
I
INJ(PIN)
does not affect the ADC
accuracy.
3. Better performance may be achieved in restricted V
DDA
, frequency and temperature ranges.
4. Data based on characterization results, not tested in production.
