ADS1610
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SBAS344C–AUGUST 2005–REVISED OCTOBER 2006
NOISE FLOOR
two samples is more than 3dB. Figure 38 below
shows the typical in-band noise spectral density of
the ADS1610. The numbers in the bottom of the
figure represent the noise distribution with respect to
a full-scale signal in different bandwidths of interest.
The shaded area represents the signal bandwidth in
the default mode of operation (10MHz output data
rate).
The ADS1610 is a delta sigma ADC and it uses
noise shaping to achieve superior SNR performance.
The noise floor of a typical successive approximation
(SAR) or a pipeline ADC remains flat until the nyquist
frequency occurs. A gain of 3dB in SNR can be
achieved by averaging two samples, thereby having
a tradeoff between output data rate and achievable
SNR. In contrast, the noise floor of the ADS1610
inside the bandwidth of interest is shaped. Hence,
the gain in SNR that can be achieved by averaging
In band
Frequency (MHz)
1
2
3
4
5
10
30
96dBFS
93dBFS
91dBFS
88.5dBFS
86dBFS
74dBFS
-
55dBFS
Figure 38. Typical Filter Bypass Mode Noise Spectral Density
By using appropriate filtering the user can achieve a tradeoff between speed and SNR. For ease of use, the
ADS1610 provides four filtering modes as explained in the next section. Figure 39 shows a conceptual diagram
of the available filtering modes. Custom filtering is achieved by taking the modulator output data and adding a
filter externally.
AIN
DOUT
5M
10M
Decimation by
2
ADS1610
Modulator
60M
20M
Mux
Decimation
by 3
Decimation
by 2
MODE[1:0]
Figure 39. Conceptual Diagram of the ADS1610 Filtering Modes
MODE SELECTION
ADS1610 offers four different modes of operation each with different output data rates. This gives users the
flexibility to choose the best output rate for their application. The outputs of all modes are MSB-aligned.
18
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