LT1461 LINER [Linear Technology], LT1461 Datasheet - Page 13

• Manufacturer Part Number: LT1461
• Description: Easy-to-Use, Ultra-Tiny, Differential, 16-Bit ADC With I2C Interface
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Signal Bandwidth, Transition Noise and Noise
Equivalent Input Bandwidth
The LTC2453 includes a sinc
notch located at f
bandwidth is 26.54Hz. The calculated LTC2453 input signal
attenuation vs frequency over a wide frequency range is
shown in Figure 12. The calculated LTC2453 input signal
attenuation vs frequency at low frequencies is shown in
Figure 13. The converter noise level is about 1.4μV
and can be modeled by a white noise source connected
at the input of a noise-free converter.
On a related note, the LTC2453 uses two separate A/D
converters to digitize the positive and negative inputs.
Each of these A/D converters has 1.4μV
noise. If one of the input voltages is within this small
transition noise band, then the output will fl uctuate one
Figure 12. LTC2453 Input Signal Attentuation vs Frequency
–100
–20
–40
–60
–80
0
0
0
= 60Hz. As such, the 3dB input signal
2.5
INPUT SIGNAL FREQUENCY (MHz)
5.0
1
type digital fi lter with the fi rst
7.5
1.00
1.25
RMS
2453 F12
1.50
transition
RMS
bit, regardless of the value of the other input voltage. If
both of the input voltages are within their transition noise
bands, the output can fl uctuate 2 bits.
For a simple system noise analysis, the V
be modeled as a single-pole equivalent circuit character-
ized by a pole location f
If the converter has an unlimited bandwidth, or at least a
bandwidth substantially larger than f
contribution of the external drive circuit would be:
Then, the total system noise level can be estimated as
the square root of the sum of (V
LTC2453 noise fl oor (~1.4μV
V
n
=
n
Figure 13. LTC2453 Input Signal Attenuation
vs Frequency (Low Frequencies)
i
π / • 2
–10
–15
–20
–25
–30
–35
–40
–45
–50
–5
0
0
60
f
i
INPUT SIGNAL FREQUENCY (Hz)
120
180
i
and a noise spectral density n
240
2
300
).
n
360 420
2
) and the square of the
i
, then the total noise
480
IN
LTC2453
540
drive circuit can
2453 F13
600
13
2453f
i
.