LTC2422CMS#TRPBF Linear Technology, LTC2422CMS#TRPBF Datasheet - Page 23

• Manufacturer Part Number: LTC2422CMS#TRPBF
• Description: IC ADC 2CH 20BIT MICRPWR 10-MSOP
• Manufacturer: Linear Technology

Specifications of LTC2422CMS#TRPBF

• Number Of Bits: 20
• Sampling Rate (per Second): 7.5
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 1mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
Input Current (V
If complete settling occurs on the input, conversion re-
sults will be uneffected by the dynamic input current. If the
settling is incomplete, it does not degrade the linearity
performance of the device. It simply results in an offset/
full-scale shift, see Figure 17. To simplify the analysis of
input dynamic current, two separate cases are assumed:
large capacitance at V
tance at V
TUE
ZS
SET
SOURCE
SIGNAL
INTPUT
IN
50
40
10
30
20
0
Figure 19. Offset vs R
(C
1
V
V
V
T
Figure 17. Offset/Full-Scale Shift
Figure 18. An RC Network at V
IN
A
CC
REF
IN
= 25 C
IN
= 0V
= 5V
< 0.01 F).
= 5V
R
)
10
SOURCE
U
C
C
IN
C
IN
IN
IN
C
= 1000pF
IN
= 100pF
= 0.01 F
100
(C
R
SOURCE
= 0pF
U
IN
C
V
IN
IN
> 0.01 F) and small capaci-
( )
1k
SOURCE
C
W
PAR
20pF
10k
(Small C)
24212 F19
IN
100k
V
LTC2421/
LTC2422
IN
24212 F17
U
FS
24212 F17
SET
If the total capacitance at V
(< 0.01 F), relatively large external source resistances (up
to 80k for 20pF parasitic capacitance) can be tolerated
without any offset/full-scale error. Figures 19 and 20 show
a family of offset and full-scale error curves for various
small valued input capacitors (C
of input source resistance.
For large input capacitor values (C
spikes are averaged by the capacitor into a DC current. The
gain shift becomes a linear function of input source resis-
tance independent of input capacitance, see Figures 21
and 22. The equivalent input impedance is 16.6M . This
results in 150nA of input dynamic current at the extreme
values of V
This corresponds to a 0.3ppm shift in offset and full-scale
readings for every 10 of input source resistance.
Figure 21. Full-Scale Error vs R
–25
–35
–15
–20
–30
–10
–5
IN
35
30
25
20
15
10
Figure 20. Offset vs R
5
0
5
0
0
0
(V
V
V
V
T
CC
REF
IN
A
IN
= 25 C
= 0V
= 5V
= 5V
200
200
= 0V and V
C
C
C
C
C
C
C
C
C
C
C
C
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
= 22 F
= 10 F
= 1 F
= 0.1 F
= 0.01 F
= 0.001 F
= 22 F
= 10 F
= 1 F
= 0.1 F
= 0.01 F
= 0.001 F
LTC2421/LTC2422
400
R
400
R
SOURCE
SOURCE
IN
IN
600
( )
600
( )
SOURCE
= V
(see Figure 18) is small
IN
< 0.01 F) as a function
IN
SOURCE
REF
V
V
V
T
800
800
CC
REF
IN
A
> 0.01 F), the input
(Large C)
= 25 C
= 0V
= 5V
, when V
= 5V
24212 F20
24212 F21
1000
(Large C)
1000
REF
23
= 5V).
24212f