Datasheet

ST72321Rx ST72321ARx ST72321Jx
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ADC CHARACTERISTICS (Cont’d)
Figure 96. R
AIN
max. vs f
ADC
with C
AIN
=0pF
1)
Figure 97. Recommended C
AIN
& R
AIN values.
2)
Figure 98. Typical A/D Converter Application
Notes:
1. C
PARASITIC
represents the capacitance of the PCB (dependent on soldering and PCB layout quality) plus the pad ca-
pacitance (3pF). A high C
PARASITIC
value will downgrade conversion accuracy. To remedy this, f
ADC
should be reduced.
2. This graph shows that depending on the input signal variation (f
AIN
), C
AIN
can be increased for stabilization time and
decreased to allow the use of a larger serial resistor (R
AIN)
.
0
5
10
15
20
25
30
35
40
45
0103070
C
PARASITIC
(pF)
Max. R
AIN
(Kohm)
2 MHz
1 MHz
0.1
1
10
100
1000
0.01 0.1 1 10
f
AIN
(KHz)
Max. R
AIN
(Kohm)
Cain 10 nF
Cain 22 nF
Cain 47 nF
AINx
ST72XXX
V
DD
I
L
±1μA
V
T
0.6V
V
T
0.6V
C
ADC
12pF
V
AIN
R
AIN
10-Bit A/D
Conversion
2kΩ(max)
C
AIN