ADS5560 datasheet(37/53 Pages) TI

37 / 53 page

S0165-08

VCM

REFM

REFP

INTREF

EXTREF

Internal

Reference

ADS556x

Programmable Fine Gain

Low Frequency Noise Suppression

ADS5560

ADS5562

www.ti.com ....................................................................................................................................................................................................... SLWS207 – MAY 2008

Figure 50. Reference Section

ADS556x has programmable fine gain from 0 dB to 6dB in steps of 1 dB. The corresponding full-scale input

range varies from 3.6VPP down to 2VPP. The fine gain is useful, when lower full-scale input ranges are used to

get SFDR improvement (See Figure 15 and Figure 31). This is accompanied by corresponding degradation in

SNR (see Figure 16 and Figure 32). The gain can be programmed using the register bits GAIN (Table 14).

After reset, the device is initialized to 1 dB fine gain.

Table 23. Full-scale Input Range Across Gains

Gain, dB

Corresponding full-scale input range, Vpp

3.56 (1)

1, default after reset

3.56

3.20

2.85

2.55

2.27

2.00

(1)

Note that with 0 dB gain, the full-scale input range continues to be 3.56Vpp. This means that the output code range will be 58409 LSBs

(or 1dB below 65536).

The low-frequency noise suppression mode is specifically useful in applications where good noise performance is

desired in the low frequency band of dc to 1 MHz. Setting this mode shifts the low-frequency noise of the

ADS556x to approximately (Fs/2), thereby moving the noise floor around dc to a much lower value. Register bit

<LF NOISE SUPPRESSION> enables this mode. As Figure 52 shows, when the mode is enabled, the noise floor

from dc-1 MHz improves significantly. The low frequency noise components get shifted to the region around Fs/2

(Figure 53).

Submit Documentation Feedback

Product Folder Link(s): ADS5560 ADS5562

ADS5560 Datasheet(PDF) 37 Page - Texas Instruments

ADS5560 Datasheet(HTML) 37 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53

Datasheet Download

Link URL