AD7008 Datasheet, PDF (1/16 Pages) Analog Devices – CMOS DDS Modulator

a
CMOS
DDS Modulator
AD7008
FEATURES
Single +5 V Supply
32-Bit Phase Accumulator
On-Chip COSINE and SINE Look-Up Tables
On-Chip 10-Bit DAC
Frequency, Phase and Amplitude Modulation
Parallel and Serial Loading
Software and Hardware Power Down Options
20 MHz and 50 MHz Speed Grades
44-Pin PLCC
APPLICATIONS
Frequency Synthesizers
Frequency, Phase or Amplitude Modulators
DDS Tuning
Digital Modulation
PRODUCT DESCRIPTION
The AD7008 direct digital synthesis chip is a numerically con-
trolled oscillator employing a 32-bit phase accumulator, sine and
cosine look-up tables and a 10-bit D/A converter integrated on a
single CMOS chip. Modulation capabilities are provided for
phase modulation, frequency modulation, and both in-phase and
quadrature amplitude modulation suitable for QAM and SSB
generation.
Clock rates up to 20 MHz and 50 MHz are supported. Fre-
quency accuracy can be controlled to one part in 4 billion.
Modulation may be effected by loading registers either through
the parallel microprocessor interface or the serial interface. A
frequency-select pin permits selection between two frequencies
on a per cycle basis.
The serial and parallel interfaces may be operated independently
and asynchronously from the DDS clock; the transfer control
signals are internally synchronized to prevent metastability prob-
lems. The synchronizer can be bypassed to reduce the transfer
latency in the event that the microprocessor clock is synchro-
nous with the DDS clock.
A power-down pin allows external control of a power-down
mode (also accessible through the microprocessor interface)
The AD7008 is available in 44-pin PLCC.
PRODUCT HIGHLIGHT
1. Low Power
2. DSP/µP Interface
3. Completely Integrated
CLOCK
FSELECT
SCLK
SDATA
FUNCTIONAL BLOCK DIAGRAM
V_AA
GND
FS ADJUST ^VREF
FREQ0 ³²
REG
32
MUX
32
12
Σ
32
FREQ1
REG
PHASE
ACCUMULATOR
12
Σ
12
32-BIT SERIAL REGISTER
PHASE REG
IQMOD [19:10]
10
10
SIN
SIN/COS
ROM
10
COS
10
10
Σ
10
10
IQMOD [9:0]
FULLSCALE
ADJUST
10-BIT DAC
32-BIT PARALLEL REGISTER
COMMAND REG
AD7008
COMP
IOUT
IOUT
MPU INTERFACE
TRANSFER LOGIC
D0
D15
WR CS
TC0
TC3 LOAD
TEST
RESET SLEEP
REV. B
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reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
© Analog Devices, Inc., 1995
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