Datasheet
LTC2483
23
2483fc
Second, the increase in clock frequency will increase
proportionally the amount of sampling charge trans-
ferred through the input and the reference pins. If large
external input and/or reference capacitors (C
IN
, C
REF
)
are used, the previous section provides formulae for
evaluating the effect of the source resistance upon the
converter performance for any value of f
EOSC
. If small
external input and/or reference capacitors (C
IN
, C
REF
) are
used, the effect of the external source resistance upon
the LTC2483 typical performance can be inferred from
Figures 9, 10, 11 and 12 in which the horizontal axis is
scaled by 307200/f
EOSC
.
applicaTions inFormaTion
Figure 20. Resolution (INL
MAX
≤ 1 LSB) vs
Output Data Rate and Temperature
OUTPUT DATA RATE (READINGS/SEC)
0
10
RESOLUTION (BITS)
12
16
18
22
10
50
70
2483 F20
14
20
40
90
100
20
30
60 80
T
A
= 85°C
T
A
= 25°C
V
IN(CM)
= V
REF(CM)
V
CC
= V
REF
= 5V
CA0/F
0
= EXT CLOCK
RES = LOG 2 (V
REF
/INL
MAX
)
Third, an increase in the frequency of the external oscil-
lator above 1MHz (a more than 3
+
increase in the output
data rate) will start to decrease the effectiveness of the
internal autocalibration circuits. This will result in a progres-
sive degradation in the converter accuracy and linearity.
Typical measured performance curves for output data rates
up to 100 readings per second are shown in Figures 16
to 23. In order to obtain the highest possible level of
accuracy from this converter at output data rates above
20 readings per second, the user is advised to maximize
the power supply voltage used and to limit the maximum
ambient operating temperature. In certain circumstances,
a reduction of the
differential reference voltage may
be beneficial.
Figure 21. Offset Error vs Output
Data Rate and Reference Voltage
OUTPUT DATA RATE (READINGS/SEC)
0
–10
OFFSET ERROR (ppm OF V
REF
)
–5
5
10
20
10
50
70
2483 F21
0
15
40
90
100
20
30
60 80
V
CC
= 5V, V
REF
= 2.5V
V
CC
= V
REF
= 5V
V
IN(CM)
= V
REF(CM)
V
IN
= 0V
CA0/F
0
= EXT CLOCK
T
A
= 25°C
Figure 22. Resolution (Noise
RMS
≤ 1 LSB)
vs Output Data Rate and Reference Voltage
OUTPUT DATA RATE (READINGS/SEC)
0
10
RESOLUTION (BITS)
12
16
18
20
24
10
50
70
2483 F22
14
22
40
90
100
20
30
60 80
V
IN(CM)
= V
REF(CM)
V
IN
= 0V
CA0/F
0
= EXT CLOCK
T
A
= 25°C
RES = LOG 2 (V
REF
/NOISE
RMS
)
V
CC
= 5V, V
REF
= 2.5V
V
CC
= V
REF
= 5V
Figure 23. Resolution (INL
MAX
≤ 1 LSB)
vs Output Data Rate and Reference Voltage
OUTPUT DATA RATE (READINGS/SEC)
0
10
RESOLUTION (BITS)
12
16
18
22
10
50
70
2483 F23
14
20
40
90
100
20
30
60 80
V
IN(CM)
= V
REF(CM)
V
IN
= 0V
CA0/F
0
= EXT CLOCK
T
A
= 25°C
RES = LOG 2 (V
REF
/INL
MAX
)
V
CC
= 5V, V
REF
= 2.5V
V
CC
= V
REF
= 5V