AD9910_07 Datasheet, PDF (16/60 Pages) Analog Devices – 1 GSPS, 14-Bit, 3.3 V CMOS Direct Digital Synthesizer

AD9910
THEORY OF OPERATION
The AD9910 has four modes of operation:
• Single tone
• RAM modulation
• Digital ramp modulation
• Parallel data port modulation
A separate output shift keying (OSK) function is also available.
This function employs a separate digital linear ramp generator
that only affects the amplitude parameter of the DDS. The OSK
function has priority over the other data sources that can drive
the DDS amplitude parameter. As such, no other data source
can drive the DDS amplitude when the OSK function is enabled.
The modes relate to the data source used to supply the DDS
with its signal control parameters: frequency, phase, or ampli-
tude. The partitioning of the data into different combinations
of frequency, phase, and amplitude is handled automatically
based on the mode and/or specific control bits.
In single tone mode, the DDS signal control parameters come
directly from the programming registers associated with the
serial I/O port. In RAM modulation mode, the DDS signal
control parameters are stored in the internal RAM and played
back upon command. In digital ramp modulation mode, the
DDS signal control parameters are delivered by a digital ramp
generator. In parallel data port modulation mode, the DDS
signal control parameters are driven directly into the parallel port.
The various modulation modes generally operate on only one of
the DDS signal control parameters (two in the case of the polar
modulation format). The unmodulated DDS signal control
parameters are stored in their appropriate programming
registers and automatically route to the DDS based on the
selected mode.
Although the various modes (including the OSK function) are
described independently, they can be enabled simultaneously.
This provides an unprecedented level of flexibility for generating
complex modulation schemes. However, to avoid multiple data
sources from driving the same DDS signal control parameter,
the device has a built-in priority protocol (see Table 5 in the
Mode Priority section).
SINGLE TONE MODE
In single tone mode, the DDS signal control parameters are
supplied directly from the programming registers. A profile is
an independent register that contains the DDS signal control
parameters. Eight profile registers are available.
Each profile is independently accessible. Use the three external
profile pins (PROFILE<2:0>) to select the desired profile. A
change in the state of the profile pins with the next rising edge
on SYNC_CLK updates the DDS with the parameters specified
by the selected profile.
2
SDIO
SCLK
I/O_RESET
CS
OSK
DRCTL ²
DRHOLD
DROVER
3
PROFILE
I/O_UPDATE
16
PARALLEL
INPUT
2
RAM_SWP_OVR
RAM
OUTPUT
SHIFT
KEYING
DIGITAL
RAMP
GENERATOR
PROGRAMMING
REGISTERS
8
DAC FSC
AD9910
DDS
8
DAC FSC
AUX
DAC
8-BIT
AMPLITUDE (A)
PHASE (θ)
DATA
ROUTE FREQUENCY (ω)
AND
PARTITION
CONTROL
A
θ
ω
CLOCK
Acos (ωt+θ)
Asin (ωt+θ)
INVERSE
SINC
FILTER
SYSCLK
÷2
INTERNAL CLOCK TIMING
AND CONTROL
PLL
DAC
14-BIT
DAC_RSET
IOUT
IOUT
REFCLK_OUT
REF_CLK
REF_CLK
TxENABLE
PDCLK
PARALLEL DATA
TIMING AND
CONTROL
POWER
DOWN
CONTROL
MULTICHIP
SYNCHRONIZATION
2
2
XTAL_SEL
Figure 22. Single Tone Mode
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