ST10F276Z5 STMicroelectronics, ST10F276Z5 Datasheet - Page 191

• Manufacturer Part Number: ST10F276Z5
• Description: 16-BIT MICROCONTROLLER WITH MAC UNIT, UP TO 832 KBYTES FLASH MEMORY AND UP TO 68 KBYTES RAM
• Manufacturer: STMicroelectronics

Specifications of ST10F276Z5

• Single Voltage Supply: 5V ±10% (embedded regulator for 1.8 V core supply)

ST10F276Z5
23.7.4
23.7.5
Analog reference pins
The accuracy of the A/D converter depends on the accuracy of its analog reference: A noise
in the reference results in proportionate error in a conversion. A low pass filter on the A/D
converter reference source (supplied through pins V
order to clean the signal, minimizing the noise. A simple capacitive bypassing may be suffi-
cient in most cases; in presence of high RF noise energy, inductors or ferrite beads may be
necessary.
In this architecture, V
cuitry 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 cir-
cuitry.
An external resistance on V
sons, series resistance is not advisable and more generally, 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, analog input pins must have low AC imped-
ance. 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; moreover, its source
charges during the sampling phase, when the analog signal source is a high-impedance
source.
A real filter is typically obtained by using a series resistance with a capacitor on the input pin
(simple RC Filter). The RC filtering may be limited according to the value of source imped-
ance of the transducer or circuit supplying the analog signal to be measured. The filter at the
input pins must be designed taking into account the dynamic characteristics of the input sig-
nal (bandwidth).
Figure 47. A/D converter input pins scheme
V
A
Source
R
R
C
R
R
R
c
C
p
R
S
F
F
L
SW
AD
S
S
EXTERNAL CIRCUIT
AREF
Source impedance
Filter resistance
Filter capacitance
Current limiter resistance
Channel selection switch impedance
Sampling switch impedance
Pin capacitance (two contributions, CP1 and CP2)
Sampling capacitance
and V
AREF
R
Filter
F
C
F
AGND
could introduce error under certain conditions: For this rea-
Current Limiter
pins also represent the power supply of the analog cir-
R
L
C
P1
AREF
and V
V
INTERNAL CIRCUIT SCHEME
DD
AGND
Selection
Channel
Electrical characteristics
R
SW
C
), is recommended in
P2
Sampling
R
AD
C
S
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