ST10F271E STMICROELECTRONICS [STMicroelectronics], ST10F271E Datasheet - Page 140

• Manufacturer Part Number: ST10F271E
• Description: 16-bit MCU with 128 Kbyte Flash memory and 8/12 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Electrical characteristics
24.7.4
140/180
Figure 39. A/D conversion characteristic
Analog reference pins
The accuracy of the A/D converter depends on how accurate is its analog reference: a noise
in the reference results in at least that much error in a conversion. A low pass filter on the
A/D converter reference source (supplied through pins V
in order to clean the signal, minimizing the noise. A simple capacitive bypassing may be
sufficient in most of the cases; in presence of high RF noise energy, inductors or ferrite
beads may be necessary.
In this architecture, V
circuitry of the A/D converter: there is an effective DC current requirement from the
reference voltage by the internal resistor string in the R-C DAC array and by the rest of the
analog circuitry.
An external resistance on V
reasons, series resistance are not advisable, and more in general any series devices in the
filter network should be designed to minimize the DC resistance.
Analog Input pins
To improve the accuracy of the A/D converter, it is definitively necessary that analog input
pins have low AC impedance. Placing a capacitor with good high frequency characteristics
at the input pin of the device, can be effective: the capacitor should be as large as possible,
ideally infinite. This capacitor contributes to attenuating the noise present on the input pin;
Digital
Out
(HEX)
Offset Error OFS
3FD
3FC
3FE
3FB
3FA
3FF
007
006
005
004
003
002
001
000
1
2
3
AREF
Ideal Characteristic
4
1 LSB (ideal)
and V
AREF
5
(7)
6
V
[LSB
AIN
(4)
AGND
could introduce error under certain conditions: for this
(3)
IDEAL
7
(LSB
(2)
(5)
IDEAL
pins represents also the power supply of the analog
= V
AREF
)
1018
/ 1024]
(6)
1020
(1)
(1) Example of an actual transfer curve
(2) The ideal transfer curve
(3) Differential Non-Linearity Error (DNL)
(4) Integral Non-Linearity Error (INL)
(5) Center of a step of the actual transfer curve
(6) Quantization Error (1/2 LSB)
(7) Total Unadjusted Error (TUE)
Offset Error OFS
AREF
1022
and V
1024
ST10F271B/ST10F271E
AGND
Bisector Characteristic
Gain Error GE
), is recommended