STRT71XF Datasheet, PDF (64/74 Pages) STMicroelectronics – ARM7TDMI™ 32-bit MCU with Flash, USB, CAN 5 timers, ADC, 10 communications interfaces

Electrical parameters
Figure 34. ADC Accuracy Characteristics
4095
4094
4093
ADC_DATA(0V)
ADC_DATA(2.5V)
(2)
(3)
(1)
STR71xF
5
4
3
2
1
0 ₁₂₃
AV_SS
1633
VCM
1LSBIDEAL
=
A_------V_-----D_------D_------–_------A_-----V_-----S_-----S_---
4095
E_L
E_D
1 LSB_IDEAL
3100 3101 3102 3103
V_AIN (LSB_IDEAL)
(1) Example of an actual transfer curve
(2) The ideal transfer curve
(3) End point correlation line
Out of range
4093 4094 4095
AV_DD
E_D=Differential Linearity Error: maximum deviation between actual steps and the
ideal one.
E_L=Integral Linearity Error: maximum deviation between any actual transition and
the end point correlation line.
Analog Power Supply and Reference Pins
The AV_DD and AV_SS pins are the analog power supply of the A/D converter cell. They act as
the high and low reference voltages for the conversion.
Separation of the digital and analog power pins allow board designers to improve A/D
performance. Conversion accuracy can be impacted by voltage drops and noise in the event
of heavily loaded or badly decoupled power supply lines (see: General PCB Design
Guidelines).
General PCB Design Guidelines
To obtain best results, some general design and layout rules should be followed when
designing the application PCB to shield the noise-sensitive, analog physical interface from
noise-generating CMOS logic signals.
● Use separate digital and analog planes. The analog ground plane should be connected
to the digital ground plane via a single point on the PCB.
● Filter power to the analog power planes. It is recommended to connect capacitors, with
good high frequency characteristics, between the power and ground lines, placing
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