ST10F272B_12 STMICROELECTRONICS [STMicroelectronics], ST10F272B_12 Datasheet - Page 144

• Manufacturer Part Number: ST10F272B_12
• Description: 16-bit MCU with 256 Kbyte Flash memory and 12/20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Electrical characteristics
24.7.4
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Figure 38. 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;
AREF
and V
AREF
Doc ID 11917 Rev 3
AGND
could introduce error under certain conditions: for this
pins represents also the power supply of the analog
AREF
and V
ST10F272B/ST10F272E
AGND
), is recommended