Datasheet

ADS58B18

ADS58B19

www.ti.com

SBAS487D – NOVEMBER 2009–REVISED JANUARY 2011

Table 9 shows the relation between each coefficient and its corner frequency. By choosing appropriate

coefficients, the bathtub can be positioned over the frequency range of 0 to f

/2 (Table 10 shows some

examples). By positioning the bathtub within the desired signal band, SNR improvement can be achieved (see

Table 4). Note that as the bandwidth is increased, the amount of SNR improvement reduces.

After a reset, the device is in low-latency disabled mode. To use the SNRBoost:

• For the required bathtub position, write the appropriate coefficients in the SNRBoost Coeff1 and SNRBoost

Coeff2 registers

• SNRBoost can be enabled or disabled using the SNRBoost_EN digital input pin. This pin has higher priority

over the SNRBoost Enable1 and SNRBoost Enable2 register bits

• To use the enable register bits, set the override bit (OVER_RIDE SNRBoost pin).

Table 9. Setting the Corner Frequency

SNRBoost COEFFICIENT NORMALIZED CORNER SNRBoost COEFFICIENT NORMALIZED CORNER

VALUE FREQUENCY (f/f

) VALUE FREQUENCY (f/f

)

7 0.42 F 0.23

6 0.385 E 0.21

5 0.357 D 0.189

4 0.333 C 0.167

3 0.311 B 0.143

2 0.29 A 0.115

1 0.27 9 0.08

0 0.25 8 0

Table 10. Positioning the Corner Frequency

SNRBoost SNRBoost

COEFFICIENT1 NORMALIZED CORNER COEFFICIENT1 NORMALIZED CORNER

(SNRBoost Coeff1) FREQUENCY1 (f/f

) (SNRBoost Coeff2) FREQUENCY2 (f/f

) CENTER FREQUENCY

0 0.25 0 0.25 f

× 0.25

F 0.23 1 0.27 f

× 0.25

6 0.385 2 0.29 f

× 0.3375

D 0.189 B 0.143 f

× 0.166

9 0.08 7 0.42 f

× 0.25

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