AD9777-EB Analog Devices Inc, AD9777-EB Datasheet - Page 34

• 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

AD9777
MODULATION, NO INTERPOLATION
With Control Register 01h, Bit 7 and Bit 6 set to 00, the
interpolation function on the AD9777 is disabled. Figure 59 to
Figure 62 show the DAC output spectral characteristics of the
AD9777 in the various modulation modes, all with the
interpolation filters disabled. The modulation frequency is
determined by the state of Control Register 01h, Bits 5 and 4.
The tall rectangles represent the digital domain spectrum of a
baseband signal of narrow bandwidth.
The Effects of Digital Modulation on DAC Output Spectrum, Interpolation Disabled
–100
–100
–20
–40
–60
–80
–20
–40
–60
–80
0
0
0
0
Figure 59. No Interpolation, Modulation Disabled
Figure 60. No Interpolation, Modulation = f
0.2
0.2
0.4
0.4
f
f
OUT
OUT
( ×
( ×
f
f
DATA
DATA
0.6
0.6
)
)
0.8
0.8
DAC
/2
1.0
1.0
Rev. C | Page 34 of 60
By comparing the digital domain spectrum to the DAC
SIN(x)/x roll-off, an estimate can be made for the characteris-
tics required for the DAC reconstruction filter. Note also, per
the previous discussion on amplitude modulation, that the
spectral components (where modulation is set to f
scaled by a factor of 2. In the situation where the modulation is
f
and there is no scaling effect.
S
/2, the modulated spectral components add constructively,
–100
–100
–20
–40
–60
–80
–20
–40
–60
–80
0
0
0
0
Figure 61. No Interpolation, Modulation = f
Figure 62. No Interpolation, Modulation = f
0.2
0.2
0.4
0.4
f
f
OUT
OUT
( ×
( ×
f
f
DATA
DATA
0.6
0.6
)
)
0.8
0.8
DAC
DAC
S
/4
/8
/4 or f
1.0
1.0
S
/8) are