Datasheet

ST72321Rx ST72321ARx ST72321Jx
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12.12 10-BIT ADC CHARACTERISTICS
Subject to general operating conditions for V
DD
, f
CPU
, and T
A
unless otherwise specified.
Notes:
1. Any added external serial resistor will downgrade the ADC accuracy (especially for resistance greater than 10kΩ). 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 I
INJ(PIN)
and ΣI
INJ(PIN)
in Section 12.8
does not affect the ADC accuracy.
Symbol Parameter Conditions Min Typ Max Unit
f
ADC
ADC clock frequency 0.4 2 MHz
V
AREF
Analog reference voltage 0.7*V
DD
≤ V
AREF
≤ V
DD
3.8 V
DD
V
V
AIN
Conversion voltage range
1)
V
SSA
V
AREF
R
AIN
External input impedance see
Figure 96
and
Figure 97
kΩ
C
AIN
External capacitor on analog input pF
f
AIN
Variation freq. of analog input signal Hz
C
ADC
Internal sample and hold capacitor 12 pF
t
ADC
Conversion time (Sample+Hold)
f
CPU
=8MHz, SPEED=0 f
ADC
=2MHz
7.5 μs
t
ADC
- No of sample capacitor loading cycles
- No. of Hold conversion cycles
4
11
1/f
ADC