ST7262 datasheet(122/139 Pages) STMICROELECTRONICS

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ADC CHARACTERISTICS (Cont’d)

12.12.1 ADC Accuracy

Table 27. fCPU=8 MHz, fADC=4 MHz RAIN< 10kΩ

Notes:

1. Not tested in production, guaranteed by characterization. All accuracy measurements are taken with the MCU in WAIT

mode (no I/O switching) and when adequate low-pass filtering is present (0.1 µF capacitor between VDD/VDDA and VSS/

VSSA). Outside these conditions, a degree of microcontroller noise may result, causing accuracy errors which will vary

based on board layout and the type of CPU activity.

2. ADC Accuracy vs. Negative Injection Current:

Injecting negative current on any of the analog input pins significantly reduces the accuracy of the conversion being per-

formed on another analog input.

For IINJ-=0.8mA, the typical leakage induced inside the die is 1.6µA and the effect on the ADC accuracy is a loss of 4 LSB

for each 10K

Ω increase of the external analog source impedance. It is recommended to add a Schottky diode (pin to

ground) to analog pins which may potentially inject negative current. Any positive injection current within the limits spec-

ified for IINJ(PIN) and ΣIINJ(PIN) in Section 12.8 does not affect the ADC accuracy.

Symbol

Parameter

Conditions

Typ

Max

Unit

|ET|

Total unadjusted error

VDD= 4V-5.5V

LSB

|EO|

Offset error

|EG|

Gain Error

0.7

|ED|

Differential linearity error

1.3

|EL|

Integral linearity error

2.9

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