AD6657ABBCZ AD [Analog Devices], AD6657ABBCZ Datasheet - Page 27

• Manufacturer Part Number: AD6657ABBCZ
• Description: Quad IF Receiver
• Manufacturer: AD [Analog Devices]

Data Sheet
36% BW MODE (>65 MHZ AT 184.32 MSPS)
The third bandwidth mode offers excellent noise performance
over 36% of the ADC sample rate (72% of the Nyquist band)
and can be centered by setting the NSR mode bits in the NSR
control register (Address 0x3C) to 010. In this mode, the useful
frequency range can be set using the 6-bit tuning word in the
NSR tuning register (Address 0x3E).
There are 28 possible tuning words (TW); each step is 0.5% of
the ADC sample rate. The following three equations describe
the left band edge (f
band edge (f
Figure 57 to Figure 59 show the typical spectrum that can be
expected from the
different tuning words.
f
f
f
0
CENTER
1
–100
–120
–140
–100
–120
–140
= f
= f
–20
–40
–60
–80
–20
–40
–60
–80
0
0
Figure 58. 36% BW Mode, Tuning Word = 14 (f
ADC
0
0
0
+ 0.36 × f
= f
1
× .005 × TW
), respectively.
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
0
Figure 57. 36% BW Mode, Tuning Word = 0
+ 0.18 × f
AD6657A
0
ADC
), the channel center (f
ADC
FREQUENCY (MHz)
FREQUENCY (MHz)
in the 36% BW mode for three
THIRD HARMONIC
THIRD HARMONIC
185MSPS
140.3MHz @ –1dBFS
NSR 36% BW MODE, TW = 14
SNR = 70.4dB (72.0dBFS)
SFDR = 91dBc
185MSPS
140.3MHz @ –1dBFS
NSR 36% BW MODE, TW = 0
SNR = 70.4dB (72.0dBFS)
SFDR = 91dBc
CENTER
S
/4 Tuning)
), and the right
Rev. 0 | Page 27 of 36
MODE PIN
The MODE pin input allows convenient control of the NSR
feature. A logic low enables NSR mode and a logic high sets the
receiver to a straight 11-bit mode with NSR disabled. By default,
the MODE pin is pulled high internally to disable the NSR.
Each channel can be individually configured to ignore the
MODE pin state by writing to Bit 4 of the NSR control register
at Address 0x3C. Use of the NSR control register in conjunction
with the MODE pin allows for very flexible control of the NSR
feature on a per channel basis.
–100
–120
–140
–20
–40
–60
–80
0
0
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
Figure 59. 36% BW Mode, Tuning Word = 28
FREQUENCY (MHz)
THIRD HARMONIC
185MSPS
140.3MHz @ –1dBFS
NSR 36% BW MODE, TW = 28
SNR = 70.4dB (72.0dBFS)
SFDR = 91dBc
AD6657A