ST72521 STMICROELECTRONICS [STMicroelectronics], ST72521 Datasheet - Page 194

• Manufacturer Part Number: ST72521
• Description: 8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST72521
10-BIT ADC CHARACTERISTICS (Cont’d)
12.12.3 ADC Accuracy
Conditions: V
Notes:
1. Injecting negative current on any of the analog input pins significantly reduces the accuracy of any conversion being
performed on any analog input.
current on digital input pins degrades ADC accuracy especially if performed on a pin close to the analog input pins.
Any positive injection current within the limits specified for I
accuracy.
2. Data based on characterization results, monitored in production.
Figure 118. ADC Accuracy Characteristics
194/211
Symbol
Analog pins can be protected against negative injection by adding a Schottky diode (pin to ground). Injecting negative
1023
1022
1021
|E
|E
|E
E
E
7
6
5
4
3
2
1
O
G
T
D
L
0
V
|
|
|
SSA
Digital Result ADCDR
1LSB
Total unadjusted error
Offset error
Gain Error
Differential linearity error
Integral linearity error
1
E
O
IDEAL
DD
2
=5V
1)
3
=
1)
Parameter
V
------------------------------------------- -
A REF
4
1024
5
–
1 LSB
1)
1)
V
SS A
E
1)
6
T
IDEAL
E
7
L
(2)
E
D
CPU in run mode @ f
CPU in run mode @ f
1021 1022 1023 1024
(3)
INJ(PIN)
(1)
Conditions
E
G
V
AREF
and I
ADC
ADC
(1) Example of an actual transfer curve
(2) The ideal transfer curve
(3) End point correlation line
E
between the actual and the ideal transfer curves.
E
transition and the first ideal one.
E
transition and the last actual one.
E
between actual steps and the ideal one.
E
between any actual transition and the end point
correlation line.
INJ(PIN)
T
O
G
D
L
=Total Unadjusted Error: maximum deviation
=Integral Linearity Error: maximum deviation
=Differential Linearity Error: maximum deviation
=Offset Error: deviation between the first actual
=Gain Error: deviation between the last ideal
2 MHz.
2 MHz.
V
in
(LSB
in
Section 12.8
IDEAL
)
Typ
-0.5
1.5
1.5
4
3
does not affect the ADC
3.5
4.5
4.5
Max
-2
2)
2)
2)
2)
Unit
LSB