ST7232A datasheet(135/154 Pages) STMICROELECTRONICS

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ST7232A

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12.12 10-BIT ADC CHARACTERISTICS

Subject to general operating conditions for VDD, fCPU, and TA unless otherwise specified.

Notes:

1. Any added external serial resistor will downgrade the ADC accuracy (especially for resistance greater than 10k

Ω). Data

based on characterization results, not tested in production.

2.injecting negative current on any of the analog input pins significantly reduces the accuracy of any conversion being

performed on any analog input. Analog pins can be protected against negative injection by adding a Schottky diode (pin

to ground). Injecting negative 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 IINJ(PIN) and ΣIINJ(PIN) in Section 12.8

does not affect the ADC accuracy.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fADC

ADC clock frequency

0.4

MHz

VAREF

Analog reference voltage

0.7*VDD ≤VAREF ≤VDD

3.8

VDD

VAIN

Conversion voltage range 1)

VSSA

VAREF

Ilkg

Positive input leakage current for analog

input 2)

-40°C

≤TA≤+85°C

±250

RAIN

External input impedance

see

Figure 78

and

Figure 79

Ω

CAIN

External capacitor on analog input

fAIN

Variation freq. of analog input signal

CADC

Internal sample and hold capacitor

tADC

Conversion time (Sample+Hold)

fCPU=8MHz, SPEED=0 fADC=2MHz

7.5

µs

tADC

- No of sample capacitor loading cycles

- No. of Hold conversion cycles

1/fADC

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