AD9767 Analog Devices, AD9767 Datasheet - Page 31

• Manufacturer Part Number: AD9767
• Manufacturer: Analog Devices

Specifications of AD9767

• Resolution (bits): 14bit
• Dac Update Rate: 125MSPS
• Dac Settling Time: 35ns
• Max Pos Supply (v): +5.5V
• Single-supply: Yes
• Dac Type: Current Out
• Dac Input Format: Par

Data Sheet
APPLICATIONS INFORMATION
VDSL EXAMPLE APPLICATIONS USING THE
AD9765 AND AD9767
Very high frequency digital subscriber line (VDSL) technology is
growing rapidly in applications requiring data transfer over
relatively short distances. By using quadrature amplitude
modulation (QAM) and transmitting the data in discrete multiple
tones (DMT), high data rates can be achieved.
As with other multitone applications, each VDSL tone is
capable of transmitting a given number of bits, depending on
the signal-to-noise ratio (SNR) in a narrow band around that
tone. For a typical VDSL application, the tones are evenly
spaced over the range of several kHz to 10 MHz. At the high
frequency end of this range, performance is generally limited by
cable characteristics and environmental factors such as external
interferers. Performance at the lower frequencies is much more
dependent on the performance of the components in the signal
chain. In addition to in-band noise, intermodulation from other
tones can also potentially interfere with the data recovery for
a given tone. The two graphs in Figure 79 and Figure 81
represent a 500-tone missing bin test vector, with frequencies
evenly spaced from 400 Hz to 10 MHz. This test is very
commonly done to determine if distortion limits the number of
bits that can be transmitted in a tone. The test vector has a
series of missing tones around 750 kHz, which is represented in
Figure 79, and a series of missing tones around 5 MHz, which is
represented in Figure 81. In both cases, the spurious-free
dynamic range (SFDR) between the transmitted tones and the
empty bins is greater than 60 dB.
Figure 79. AD9765 Notch in Missing Bin at 750 kHz Is Down >60 dB
–100
–110
–120
–20
–30
–40
–50
–60
–70
–80
–90
0.665
0.685
0.705
(Peak Amplitude = 0 dBm)
0.725
FREQUENCY (MHz)
0.745
0.765
0.785
0.805
0.825
Rev. G | Page 31 of 44
Figure 80. AD9767 Notch in Missing Bin at 750 kHz Is Down >60 dB
Figure 81. AD9765 Notch in Missing Bin at 5 MHz Is Down >60 dB
Figure 82. AD9767 Notch in Missing Bin at 5 MHz Is Down >60 dB
–100
–110
–120
–100
–120
–100
–110
–120
–30
–40
–50
–60
–70
–80
–90
–20
–40
–60
–80
–20
–30
–40
–50
–60
–70
–80
–90
4.85
4.85
0.665
0.685
4.90
4.90
0.705
(Peak Amplitude = 0 dBm)
(Peak Amplitude = 0 dBm)
(Peak Amplitude = 0 dBm)
4.95
4.95
AD9763/AD9765/AD9767
0.725
FREQUENCY (MHz)
FREQUENCY (MHz)
FREQUENCY (MHz)
0.745
5.00
5.00
0.765
5.05
5.05
0.785
0.805
5.10
5.10
0.825
5.15
5.15