LTC2410CGN Linear Technology, LTC2410CGN Datasheet - Page 32

• Manufacturer Part Number: LTC2410CGN
• Description: IC ADC 24BIT DIFF INP/REF 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC2410CGN

• Number Of Bits: 24
• 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: 16-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q894257

APPLICATIO S I FOR ATIO
LTC2410
When external amplifiers are driving the LTC2410, the
ADC input referred system noise calculation can be simpli-
fied by Figure 36. The noise of an amplifier driving the
LTC2410 input pin can be modeled as a band limited white
noise source. Its bandwidth can be approximated by the
bandwidth of a single pole lowpass filter with a corner
frequency f
From Figure 36, using f
on the y-axis the noise equivalent bandwidth freq
input driving amplifier. This bandwidth includes the band
limiting effects of the ADC internal calibration and filtering.
The noise of the driving amplifier referred to the converter
input and including all these effects can be calculated as
N = n
LTC2410 input) can now be obtained by summing as
square root of sum of squares the three ADC input referred
noise sources: the LTC2410 internal noise (800nV), the
noise of the IN
driving amplifier.
If the F
f
x-axis is scaled by f
ratio f
decrease, but in the same time the LTC2410 noise floor
rises and the noise contribution of the driving amplifiers
lose significance.
Normal Mode Rejection and Antialiasing
One of the advantages delta-sigma ADCs offer over con-
ventional ADCs is on-chip digital filtering. Combined with
a large oversampling ratio, the LTC2410 significantly
simplifies antialiasing filter requirements.
The Sinc
mode rejection at all frequencies except DC and integer
multiples of the modulator sampling frequency (f
LTC2410’s autocalibration circuits further simplify the
antialiasing requirements by additional normal mode sig-
nal filtering both in the analog and digital domain. Inde-
pendent of the operating mode, f
f
the maximum output data rate. In the internal oscillator
mode with a 50Hz notch setting, f
60Hz notch setting f
mode, f
32
EOSC
OUTMAX
, Figure 36 can still be used for noise calculation if the
i
EOSC
O
• freq
S
pin is driven by an external oscillator of frequency
4
where f
= f
digital filter provides greater than 120dB normal
/153600, the Figure 36 plot accuracy begins to
i
. The amplifier noise spectral density is n
EOSC
i
. The total system noise (referred to the
+
driving amplifier and the noise of the IN
N
/10.
in the notch frequency and f
U
S
EOSC
= 15360Hz. In the external oscillator
i
as the x-axis selector, we can find
/153600. For large values of the
U
S
S
= 12800Hz and with a
W
= 256 • f
N
OUTMAX
U
= 2048 •
S
i
). The
of the
is
i
–
.
–100
–110
–120
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
Figure 36. Input Referred Noise Equivalent Bandwidth
of an Input Connected White Noise Source
0
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
Figure 38. Input Normal Mode Rejection, Internal
Oscillator and 60Hz Notch or External Oscillator
f
S
Figure 37. Input Normal Mode Rejection,
Internal Oscillator and 50Hz Notch
–100
–110
–120
2f
100
–10
–20
–30
–40
–50
–60
–70
–80
–90
0.1
S
10
1
0
3f
0.1
0 f
DIFFERENTIAL INPUT SIGNAL FREQUENCY (Hz)
S
4f
S
S
INPUT NOISE SOURCE SINGLE POLE
F
1
O
2f
EQUIVALENT BANDWIDTH (Hz)
5f
= HIGH
S
S
3f
10
6f
S
S
4f
S
7f
100
5f
S
F
F
S
O
O
8f
6f
= LOW
= HIGH
S
S
1k
7f
9f
2410 F38
S
S
8f
10f
10k 100k
S
S
9f
F
F
f
EOSC
S
O
O
10f
= LOW OR
= EXTERNAL OSCILLATOR,
S
= 10 • f
11f
2410 F36
2410 F37
S
12f
1M
S
S