AD9777-EB Analog Devices Inc, AD9777-EB Datasheet - Page 37

• Manufacturer Part Number: AD9777-EB
• Description: BOARD EVAL FOR AD9777
• Manufacturer: Analog Devices Inc
• Series: TxDAC+®r

Specifications of AD9777-EB

• Rohs Status: RoHS non-compliant
• Number Of Dac's: 2
• Number Of Bits: 16
• Outputs And Type: 2, Differential
• Sampling Rate (per Second): 160M
• Data Interface: Parallel
• Settling Time: 11ns
• Dac Type: Current
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9777

MODULATION, INTERMODULATION = 8×
With Control Register 01h, Bits 7 and 6, set to 11, the
interpolation rate of the AD9777 is 8×. Modulation is achieved
by multiplying successive samples at the interpolation filter
output by the sequence (0, +0.707, +1, +0.707, 0, –0.707, −1,
+0.707). Figure 71 to Figure 74 represent the spectral response
of the AD9777 DAC output with 8× interpolation in the various
modulation modes to a narrow band baseband signal.
The Effects of the Digital Modulation on the DAC Output Spectrum, Interpolation = 8×
–100
–100
–20
–40
–60
–80
–20
–40
–60
–80
0
0
0
0
Figure 71. 8× Interpolation, Modulation Disabled
Figure 72. 8x Interpolation, Modulation = f
1
1
f
f
OUT
OUT
( ×
( ×
2
2
f
f
DATA
DATA
)
)
3
3
DAC
/2
4
4
Rev. C | Page 37 of 60
Looking at Figure 59 to Figure 75, the user can see how higher
interpolation rates reduce the complexity of the reconstruction
filter needed at the DAC output. It also becomes apparent that
the ability to modulate by f
flexibility in frequency planning
–100
–100
–20
–40
–60
–80
–20
–40
–60
–80
0
0
0
0
Figure 73. 8x Interpolation, Modulation = f
Figure 74. 8x Interpolation, Modulation = f
1
1
2
2
3
3
f
f
S
OUT
OUT
/2, f
(×
( ×
4
4
S
f
f
/4, or f
DATA
DATA
)
)
5
5
S
/8 adds a degree of
6
6
DAC
DAC
7
7
/4
/8
AD9777
8
8