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NOISE FLOOR

30

5

Frequency(MHz)

1

2

3

4

-

Inband

96dBFS

93dBFS

91dBFS

88.5dBFS

86dBFS

74dBFS

10

55dBFS

ADS1610

Modulator

Decimation

by3

Decimationby

2

Decimation

by2

AIN

MODE[1:0]

Mux

60M

20M

10M

5M

DOUT

MODE SELECTION

ADS1610

SBAS344C – AUGUST 2005 – REVISED OCTOBER 2006

two samples is more than 3dB. Figure 38 below

shows the typical in-band noise spectral density of

The ADS1610 is a delta sigma ADC and it uses

the ADS1610. The numbers in the bottom of the

noise shaping to achieve superior SNR performance.

figure represent the noise distribution with respect to

The noise floor of a typical successive approximation

a full-scale signal in different bandwidths of interest.

(SAR) or a pipeline ADC remains flat until the nyquist

The shaded area represents the signal bandwidth in

frequency occurs. A gain of 3dB in SNR can be

the default mode of operation (10MHz output data

achieved by averaging two samples, thereby having

rate).

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

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.

Figure 39. Conceptual Diagram of the ADS1610 Filtering Modes

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.

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