LTC2414 LINER [Linear Technology], LTC2414 Datasheet - Page 32

• Manufacturer Part Number: LTC2414
• Description: 8-/16-Channel 24-Bit No Latency TM ADCs
• Manufacturer: LINER [Linear Technology]

Figure 29. Resolution (Noise
Output Data Rate and Reference Voltage
LTC2414/LTC2418
APPLICATIO S I FOR ATIO
Due to the complex filtering and calibration algorithms
utilized, the converter input bandwidth is not modeled very
accurately by a first order filter with the pole located at the
3dB frequency. When the internal oscillator is used, the
shape of the LTC2414/LTC2418 input bandwidth is shown
in Figure 31 for F
oscillator of frequency f
LTC2414/LTC2418 input bandwidth can be derived from
Figure 31, F
scaled by f
The conversion noise (1µV
be modeled by a white noise source connected to a noise
32
Figure 26. Resolution (Noise
vs Output Data Rate and Temperature
24
23
22
21
20
19
18
17
16
15
14
13
12
24
23
22
21
20
19
18
17
16
15
14
13
12
0
0
V
REF
REF
V
V
SDI = GND
F
RESOLUTION = LOG
V
REF
V
V
SDI = GND
F
T
RESOLUTION = LOG
O
CC
INCM
IN
O
A
CC
INCM
IN
10 20 30 40 50 60 70 80 90 100
10 20 30 40 50 60 70 80 90 100
OUTPUT DATA RATE (READINGS/SEC)
= EXTERNAL OSCILLATOR
OUTPUT DATA RATE (READINGS/SEC)
= EXTERNAL OSCILLATOR
= 25°C
+
= 0V
–
= 5V
= 0V
–
= 5V
= 5V
= GND
= GND
= 2.5V
= 2.5V
EOSC
O
= LOW curve in which the horizontal axis is
V
/153600.
REF
O
= LOW and F
= 2.5V
T
2
2
A
(V
U
(V
= 85°C
REF
V
REF
REF
/NOISE
/NOISE
= 5V
RMS
EOSC
T
RMS
U
A
RMS
= 25°C
RMS
RMS
≤ 1LSB) vs
≤ 1LSB)
)
2414/18 F26
O
)
is used, the shape of the
2414/18 F29
typical for V
= HIGH. When an external
W
Figure 27. Resolution (INL
vs Output Data Rate and Temperature
Figure 30. Resolution (INL
Output Data Rate and Reference Voltage
22
20
18
16
14
12
10
22
20
18
16
14
12
10
8
REF
8
0
0
V
REF
REF
V
–2.5V < V
SDI = GND
F
T
V
REF
V
–0.5V • V
SDI = GND
F
U
O
RESOLUTION = LOG
CC
INCM
O
A
CC
INCM
= 5V) can
10 20 30 40 50 60 70 80 90 100
10 20 30 40 50 60 70 80 90 100
OUTPUT DATA RATE (READINGS/SEC)
= EXTERNAL OSCILLATOR
T
OUTPUT DATA RATE (READINGS/SEC)
= 25°C
= EXTERNAL OSCILLATOR
+
= 5V
–
A
–
V
= 5V
= 5V
= GND
REF
= 85°C
= GND
= 2.5V
= 0.5 • REF
IN
REF
= 2.5V
< 2.5V
< V
IN
+
T
< 0.5 • V
A
= 25°C
2
(V
RESOLUTION =
LOG
V
free converter. The noise spectral density is 78nV/√Hz for
an infinite bandwidth source and 107nV/√Hz for a single
0.5MHz pole source. From these numbers, it is clear that
particular attention must be given to the design of external
amplification circuits. Such circuits face the simultaneous
requirements of very low bandwidth (just a few Hz) in
order to reduce the output referred noise and relatively
high bandwidth (at least 500kHz) necessary to drive the
input switched-capacitor network. A possible solution is a
high gain, low bandwidth amplifier stage followed by a
high bandwidth unity-gain buffer.
REF
REF
2
REF
/INL
(V
= 5V
RMS
REF
MAX
MAX
/INL
≤ 1LSB)
)
≤ 1LSB) vs
MAX
2414/18 F27
2414/18 F30
)
–0.5
–1.0
–1.5
–2.0
–2.5
–3.0
–3.5
–4.0
–4.5
–5.0
–5.5
–6.0
0.0
200
150
100
–50
50
0
Figure 28. Offset Error vs Output
Data Rate and Reference Voltage
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
0
Figure 31. Input Signal Bandwidth
Using the Internal Oscillator
F
V
REF
V
V
SDI = GND
T
O
A
CC
IN
INCM
10 20 30 40 50 60 70 80 90 100
= EXTERNAL OSCILLATOR
= 25°C
OUTPUT DATA RATE (READINGS/SEC)
–
= 0V
= 5V
= GND
= 2.5V
F
O
= HIGH
V
F
O
REF
= LOW
= 2.5V
V
REF
2414/18 F31
= 5V
2414/18 F28
241418fa