AD9775-EBZ Analog Devices Inc, AD9775-EBZ Datasheet - Page 31

• Manufacturer Part Number: AD9775-EBZ
• Description: 14Bit 160 MSPS Dual TxDAC+ D/A Converter
• Manufacturer: Analog Devices Inc
• Series: TxDAC+®r

Specifications of AD9775-EBZ

• Number Of Dac's: 2
• Number Of Bits: 14
• 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: AD9775
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

It is possible to invert the I and Q selection by setting control
Register 0x02, Bit 1 to the invert state (Logic 1). Figure 56
illustrates the timing requirements for the data inputs as well as
the IQSEL input. Note that the 1× interpolation rate is not
available in the one-port mode.
One-port mode is very useful when interfacing with devices
such as the Analog Devices AD6622 or AD6623 transmit signal
processors, in which two digital data channels have been
interleaved (multiplexed).
The programmable modes’ ONEPORTCLK inversion,
ONEPORTCLK driver strength, and IQ pairing described in
the PLL Enabled, One-Port Mode section have identical
functionality with the PLL disabled.
DIGITAL FILTER MODES
The I and Q datapaths of the AD9775 have their own
independent half-band FIR filters. Each datapath consists of
three FIR filters, providing up to 8× interpolation for each
channel. The rate of interpolation is determined by the state of
Control Register 0x01, Bit 7 and Bit 6. Figure 2 to Figure 4 show
the response of the digital filters when the AD9775 is set to 2×,
4×, and 8× modes. The frequency axes of these graphs are
normalized to the input data rate of the DAC. As the graphs
show, the digital filters can provide greater than 75 dB of
out-of-band rejection.
An online tool is available for quick and easy analysis of the
AD9775 interpolation filters in the various modes. The link can
be accessed at
AMPLITUDE MODULATION
Given two sine waves at the same frequency, but with a
90 degree phase difference, a point of view in time can be taken
such that the waveform that leads in phase is cosinusoidal and
the waveform that lags is sinusoidal. Analysis of complex
variables states that the cosine waveform can be defined as
having real positive and negative frequency components, while
the sine waveform consists of imaginary positive and negative
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frequency images. This is shown graphically in the frequency
domain in Figure 57.
Amplitude modulating a baseband signal with a sine or a cosine
convolves the baseband signal with the modulating carrier in
the frequency domain. Amplitude scaling of the modulated
signal reduces the positive and negative frequency images by a
factor of 2.
This scaling is very important in the discussion of the various
modulation modes. The phase relationship of the modulated
signals is dependent on whether the modulating carrier is
sinusoidal or cosinusoidal, again with respect to the reference
point of the viewer. Examples of sine and cosine modulation are
given in Figure 58.
Ae
Ae
–jωt
–jωt
/2j
/2
Figure 58. Baseband Signal, Amplitude Modulated
e
e
–jωt
Figure 57. Real and Imaginary Components of
–jωt
Sinusoidal and Cosinusoidal Waveforms
/2j
/2
with Sine and Cosine Carriers
DC
DC
DC
DC
Ae
Ae
–jωt
–jωt
e
e
–jωt
–jωt
SINE
COSINE
/2j
/2
/2j
/2
SINUSOIDAL
MODULATION
COSINUSOIDAL
MODULATION
AD9775