400 MSPS 14-Bit, 1.8 V CMOS
Direct Digital Synthesizer
AD9951
Rev. 0
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FEATURES
400 MSPS internal clock speed
Integrated 14-bit DAC
32-bit tuning word
Phase noise ≤ –120 dBc/Hz @ 1 kHz offset (DAC output)
Excellent dynamic performance
>80 dB SFDR @ 160 MHz (±100 kHz offset) A
OUT
Serial I/O control
1.8 V power supply
Software and hardware controlled power-down
48-lead TQFP/EP package
Support for 5 V input levels on most digital inputs
PLL REFCLK multiplier (4× to 20×)
Internal oscillator, can be driven by a single crystal
Phase modulation capability
Multichip synchronization
APPLICATIONS
Agile LO frequency synthesis
Programmable clock generators
Test and measurement equipment
Acousto-optic device drivers
FUNCTIONAL BLOCK DIAGRAM
COS(X)
CONTROL REGISTERS
OSCILLATOR/BUFFER
SYNC
ENABLE
I/O UPDATE
DAC_R
SET
DDS CORE
PHASE
OFFSET
PHASE
ACCUMULATOR
Z
–1
Z
–1
IOUT
IOUT
OSK
PWRDWNCTL
REFCLK
REFCLK
CRYSTAL OUT I/O PORTPS<1:0>
DDS CLOCK
FREQUENCY
TUNING WORD
CLEAR PHASE
ACCUMULATOR
AMPLITUDE
SCALE FACTOR
DAC
SYSTEM
CLOCK
SYSTEM
CLOCK
SYNC_IN
SYNC_CLK
RESET
TIMING AND CONTROL LOGIC
4×–20×
CLOCK
MULTIPLIER
÷ 4
AD9951
32
32
14
14
19 14
0
M
U
X
M
U
X
03359-0-001
Figure 1.
