Datasheet

ADS58B18
ADS58B19
SBAS487D – NOVEMBER 2009– REVISED JANUARY 2011 www.ti.com
GAIN FOR SFDR/SNR TRADE-OFF
The ADS58B18/19 include gain settings that can be used to get improved SFDR performance. The gain is
programmable from 0dB to 3.5dB (in 0.5dB steps) using the GAIN register bits. For each gain setting, the analog
input full-scale range scales proportionally, as shown in Table 11.
The SFDR improvement is achieved at the expense of SNR; for each gain setting, the SNR degrades
approximately between 0.5dB and 1dB. The SNR degradation is reduced at high input frequencies. As a result,
the gain is very useful at high input frequencies because the SFDR improvement is significant with marginal
degradation in SNR. Therefore, the gain can be used to trade-off between SFDR and SNR.
After a reset, the device is in low-latency disabled mode and gain is enabled with 0dB gain. For other gain
settings, program the GAIN bits.
Table 11. Full-Scale Range Across Gains
GAIN (dB) TYPE FULL-SCALE (V
PP
)
0 Default after reset 1.5
0.5 1.41
1 1.33
1.5 1.26
2 Programmable gain 1.19
2.5 1.12
3 1.06
3.5 1
50 Submit Documentation Feedback © 2009–2011, Texas Instruments Incorporated
Product Folder Link(s): ADS58B18 ADS58B19