AD6677 datasheet(24/48 Pages) AD

24 / 48 page

AD6677

Data Sheet

Rev. C | Page 24 of 48

33% BANDWIDTH MODE (>60 MHz AT

184.32 MSPS)

The second bandwidth mode offers excellent noise performance

over 33% of the ADC sample rate (66% of the Nyquist band) and

can be centered by setting the NSR mode bit in the NSR control

range can be set using the 6-bit tuning word in the NSR tuning

each step is 0.5% of the ADC sample rate. The following three

equations describe the left band edge (f0), the channel center

(fCENTER), and the right band edge (f1), respectively:

f0 = fADC × .005 × TW

fCENTER = f0 + 0.165 × fADC

f1 = f0 + 0.33 × fADC

Figure 48 to Figure 50 show the typical spectrum that can be

expected from the AD6677 in the 33% bandwidth mode for

three different tuning words.

100

125

FREQUENCY (Hz)

–140

–120

–100

–80

–60

–40

–20

250MSPS

180.1MHz AT –1.6dBFS

SNR = 70.7dB (72.3dBFS)

SFDR = 88dBc (IN-BAND)

Figure 48. 33% Bandwidth Mode, Tuning Word = 5

FREQUENCY (Hz)

–140

–120

–100

–80

–60

–40

–20

100

125

250MSPS

180.1MHz AT –1.6dBFS

SNR = 70.8dB (72.4dBFS)

SFDR = 90dBc (IN-BAND)

Figure 49. 33% Bandwidth Mode, Tuning Word = 17 (fS/4 Tuning)

–140

–120

–100

–80

–60

–40

–20

100

125

FREQUENCY (Hz)

250MSPS

180.1MHz AT –1.6dBFS

SNR = 70.6dB (72.2dBFS)

SFDR = 88dBc (IN-BAND)

Figure 50. 33% Bandwidth Mode, Tuning Word = 27

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