SBAS603B Data sheet

SBAS603B April 2013 – November 2020 ADS4449

PRODUCTION DATA

Package Options

Mechanical Data (Package|Pins)

ZCR|144
- MPBGA77A

Thermal pad, mechanical data (Package|Pins)

Orderable Information

8.3.2 Gain for SFDR and SNR Trade-Off

The device includes gain settings that can be used to obtain improved SFDR performance. The gain is programmable from 0 dB to 6 dB (in 0.5-dB steps) using the DIGITAL GAIN CH X register bits. For each gain setting, the analog input full-scale range scales proportionally, as shown in Table 8-1.

Table 8-1 Full-Scale Range Across Gains

GAIN (dB)	TYPE	FULL-SCALE (V_PP)
0	Default after reset	2
0.5	Fine, programmable	1.89
1	Fine, programmable	1.78
1.5	Fine, programmable	1.68
2	Fine, programmable	1.59
2.5	Fine, programmable	1.5
3	Fine, programmable	1.42
3.5	Fine, programmable	1.34
4	Fine, programmable	1.26
4.5	Fine, programmable	1.19
5	Fine, programmable	1.12
5.5	Fine, programmable	1.06
6	Fine, programmable	1

SFDR improvement is achieved at the expense of SNR; for each gain setting, SNR degrades by approximately 0.5 dB to 1 dB. SNR degradation is diminished at high input frequencies. As a result, fine gain is very useful at high input frequencies because SFDR improvement is significant with marginal degradation in SNR. Therefore, fine gain can be used to trade-off between SFDR and SNR.

After a reset, the gain function is disabled. To use fine gain:

First, program the DIGITAL ENABLE bits to enable digital functions.
This setting enables the gain for all four channels and places the device in a 0-dB gain mode.
For other gain settings, program the DIGITAL GAIN CH X register bits.