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參數(shù)資料
| 型號： | AD9830 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | XO, clock |
| 英文描述： | CMOS Complete DDS |
| 中文描述： | 完整的DDS的CMOS |
| 文件頁數(shù)： | 10/16頁 |
| 文件大?。?/td> | 218K |
| 代理商： | AD9830 |
AD9830
REV. A
–10–
CIRCUIT DE SCRIPT ION
T he AD9830 provides an exciting new level of integration
for the RF/Communications system designer. T he AD9830
combines the Numerical Controlled Oscillator (NCO), SINE
Look-Up table, Frequency and Phase Modulators, and a
Digital-to-Analog Converter on a single integrated circuit.
T he internal circuitry of the AD9830 consists of three main
sections. T hese are:
Numerical Controlled Oscillator (NCO) + Phase Modulator
SINE Look-Up T able
Digital-to-Analog Converter
T he AD9830 is a fully integrated Direct Digital Synthesis
(DDS) chip. T he chip requires one reference clock, two low
precision resistors and eight decoupling capacitors to provide
digitally created sine waves up to 25 MHz. In addition to the
generation of this RF signal, the chip is fully capable of a broad
range of simple and complex modulation schemes. T hese
modulation schemes are fully implemented in the digital do-
main allowing accurate and simple realization of complex
modulation algorithms using DSP techniques.
T HE ORY OF OPE RAT ION
Sine waves are typically thought of in terms of their magnitude
form a (t) = sin (
ω
t). However, these are nonlinear and not
easy to generate except through piece wise construction. On
the other hand, the angular information is linear in nature.
T hat is, the phase angle rotates through a fixed angle for each
unit of time. T he angular rate depends on the frequency of the
signal by the traditional rate of
ω
= 2
π
f
MAGNITUDE
PHASE
+1
0
–1
2
π
0
Figure 22. Sine Wave
K nowing that the phase of a sine wave is linear and given a ref-
erence interval (clock period), the phase rotation for that period
can be determined.
Phase
=
ωδ
t
Solving for
ω
ω
=
Phase
/
δ
t = 2
π
f
Solving for f and substituting the reference clock frequency for
the reference period (1/f
MCLK
=
δ
t)
f =
Phase
×
f
MCLK
/2
π
T he AD9830 builds the output based on this simple equation.
A simple DDS chip can implement this equation with three
major subcircuits.
Numerical Controlled Oscillator + Phase Modulator
T his consists of two frequency select registers, a phase accumu-
lator and four phase offset registers. T he main component of
the NCO is a 32-bit phase accumulator which assembles the
phase component of the output signal. Continuous time signals
have a phase range of 0 to 2
π
. Outside this range of numbers,
the sinusoid functions repeat themselves in a periodic manner.
T he digital implementation is no different. T he accumulator
simply scales the range of phase numbers into a multibit digital
word. T he phase accumulator in the AD9830 is implemented
with 32 bits. T herefore, in the AD9830, 2
π
= 2
32
. Likewise,
the
Phase
term is scaled into this range of numbers 0 <
Phase
< 2
32
–1. Making these substitutions into the equation above
f =
Phase
×
f
MCLK
/2
32
where 0 <
Phase
< 2
32
With a clock signal of 50 MHz and a phase word of 051EB852
hex
f = 51EB852
×
50 MHz/2
32
= 1.000000000931 MHz
T he input to the phase accumulator (i.e., the phase step) can be
selected either from the FREQ0 Register or FREQ1 Register
and this is controlled by the FSELECT pin. NCOs inherently
generate continuous phase signals, thus avoiding any output
discontinuity when switching between frequencies. More com-
plex frequency modulation schemes can be implemented by up-
dating the contents of these registers. T his facilitates complex
frequency modulation schemes, such as GMSK .
Following the NCO, a phase offset can be added to perform
phase modulation using the 12-bit PHASE Registers. T he con-
tents of this register are added to the most significant bits of the
NCO. T he AD9830 has four PHASE registers. T he resolution
of the phase registers equals 2
π
/4096.
Sine Look-Up T able (LUT )
T o make the output useful, the signal must be converted from
phase information into a sinusoidal value. Since phase informa-
tion maps directly into amplitude, a ROM LUT converts the
phase information into amplitude. T o do this, the digital phase
information is used to address a sine ROM LUT . Although the
NCO contains a 32-bit phase accumulator, the output of the
NCO is truncated to 12 bits. Using the full resolution of the
phase accumulator is impractical and unnecessary as this would
require a look-up table of 2
32
entries.
It is necessary only to have sufficient phase resolution in the
LUT s such that the dc error of the output waveform is domi-
nated by the quantization error in the DAC. T his requires the
look-up table to have two more bits of phase resolution than the
10-bit DAC.
Digital-to-Analog Converter
T he AD9830 includes a high impedance current source 10-bit
DAC, capable of driving a wide range of loads at different
speeds. Full-scale output current can be adjusted, for optimum
power and external load requirements, through the use of a
single external resistor (R
SET
).
T he DAC can be configured for single or differential ended op-
eration.
IOUT
can be tied directly to AGND for single ended
operation or through a load resistor to develop an output volt-
age. T he load resistor can be any value required, as long as the
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| AD9830AST | CMOS Complete DDS |
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| AD9831AST | CMOS Complete DDS |
| AD9832 | CMOS Complete DDS |
| AD9832BRU | CMOS Complete DDS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD9830AST | 制造商:Analog Devices 功能描述:Direct Digital Synthesizer 50MHz 1-DAC 10-Bit Parallel 48-Pin LQFP 制造商:Rochester Electronics LLC 功能描述:50 MHZ 10-BIT DDS DAC I.C. - Tape and Reel 制造商:Analog Devices 功能描述:IC 10BIT DAC DDS 50 MHZ SMD 9830 |
| AD9830AST-REEL | 制造商:Analog Devices 功能描述:Direct Digital Synthesizer 50MHz 1-DAC 10-Bit Parallel 48-Pin LQFP T/R 制造商:Rochester Electronics LLC 功能描述:50 MHZ 10-BIT DDS DAC I.C. - Tape and Reel |
| AD9830ASTZ | 功能描述:IC DDS 10BIT 50MHZ CMOS 48-TQFP RoHS:是 類別:集成電路 (IC) >> 接口 - 直接數(shù)字合成 (DDS) 系列:- 產(chǎn)品變化通告:Product Discontinuance 27/Oct/2011 標(biāo)準(zhǔn)包裝:2,500 系列:- 分辨率（位）:10 b 主 fclk:25MHz 調(diào)節(jié)字寬（位）:32 b 電源電壓:2.97 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:16-TSSOP 包裝:帶卷 (TR) |
| AD9830ASTZ-REEL | 功能描述:IC DDS 10BIT 50MHZ CMOS 48TQFP RoHS:是 類別:集成電路 (IC) >> 接口 - 直接數(shù)字合成 (DDS) 系列:- 產(chǎn)品變化通告:Product Discontinuance 27/Oct/2011 標(biāo)準(zhǔn)包裝:2,500 系列:- 分辨率（位）:10 b 主 fclk:25MHz 調(diào)節(jié)字寬（位）:32 b 電源電壓:2.97 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-TSSOP（0.173"，4.40mm 寬） 供應(yīng)商設(shè)備封裝:16-TSSOP 包裝:帶卷 (TR) |
| AD9831 | 制造商:AD 制造商全稱:Analog Devices 功能描述:CMOS Complete DDS |
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