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參數(shù)資料
| 型號(hào)： | AD9858FDPCB |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | XO, clock |
| 英文描述： | 1 GSPS Direct Digital Synthesizer |
| 中文描述： | 1 GSPS的直接數(shù)字頻率合成器 |
| 文件頁數(shù)： | 15/32頁 |
| 文件大小： | 1412K |
| 代理商： | AD9858FDPCB |
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AD9858
THEORY OF OPERATION
OVERVIEW
The AD9858 direct digital synthesizer (DDS) is a flexible device
that can address a wide range of applications. The device
consists of an NCO with a 32-bit phase accumulator, 14-bit
phase offset adjustment, a power efficient DDS core, and a one
giga-samples per second (1 GSPS) 10-bit digital-to-analog
converter. The AD9858 incorporates additional capabilities for
automated frequency sweeping. The device also offers an analog
mixer capable of operating at 2 GHz, a phase-frequency
detector (PFD), and a programmable charge pump (CP) with
advanced fast-lock capability. These RF building blocks can be
used for various frequency synthesis loops or as needed in
system design.
Rev. A | Page 15 of 32
The AD9858 can directly generate frequencies up to 400+ MHz
when driven at a 1 GHz internal clock speed. This clock can be
derived from an external clock source of up to 2 GHz by using
the on-chip divide-by-2 feature. The on-chip mixer and
PFD/CP make possible a variety of synthesizer configurations
capable of generating frequencies in the 1 GHz to 2 GHz range
or higher.
The AD9858 offers the advantages of a DDS with the additional
flexibility to work in concert with analog frequency synthesis
techniques (PLL, mixing) to generate precision frequency
signals with high frequency resolution, fast frequency hopping,
fast settling time, and automated frequency sweeping
capabilities.
Writing data to its on-chip digital registers that control all
operations of the device easily configures the AD9858. The
AD9858 offers a choice of both serial and parallel ports for
controlling the device. Four user profiles can be selected by a
pair of external pins. These profiles allow independent setting
of the frequency tuning word and the phase offset adjustment
word for each of four selectable configurations.
The AD9858 can be programmed to operate in single-tone
mode or in frequency-sweeping mode. To save on power
consumption, there is also a programmable full-sleep mode,
during which most of the device is powered down to reduce
current flow.
available from Analog Devices at www.analog.com/dds
.
COMPONENT BLOCKS
DDS Core
The DDS core generates the numeric values that represent a
sinusoid in the digital domain. Depending on the operating
mode of the DDS, this sinusoid may be changed in frequency,
phase, or perhaps modulated by an information carrying signal.
The frequency of the output signal is determined by a user-
programmed frequency tuning word (FTW). The relation of the
output frequency of the device to the system clock (SYSCLK) is
determined by the following equation:
(
)
N
O
SYSCLK
2
FTW
F
×
=
where for the AD9858,
N
= 32.
For a more detailed explanation of a DDS core, consult the DDS
tutorial at
www.analog.com/dds
.
DAC Output
The AD9858 incorporates an integrated 10-bit current output
DAC. Two complementary outputs provide a combined full-
scale output current (I
OUT
). Differential outputs reduce the
amount of common-mode noise that might be present at the
DAC output, offering the advantage of an increased signal-to-
noise ratio. The full-scale current is controlled by means of an
external resistor (R
SET
) connected between the DACISET pin
and analog ground. The full-scale current is proportional to the
resistor value as follows:
OUT
SET
I
R
/
19
.
39
=
The maximum full-scale output current of the combined DAC
outputs is 40 mA, but limiting the output to 20 mA provides the
best spurious-free dynamic range (SFDR) performance. The
DAC output compliance range is (AV
DD
– 1.5 V) to
(AV
DD
+ 0.5 V). Voltages developed beyond this range cause
excessive DAC distortion and could potentially damage the
DAC output circuitry. Proper attention should be paid to the
load termination to keep the output voltage within this
compliance range. When terminating the differential outputs
into a transformer, the center tap should be attached to AV
DD
.
PLL Frequency Synthesizer
The PLL frequency synthesizer is a group of independent
synthesis blocks, designed to be used with the DDS to expand
the range of synthesis applications. These blocks are a digital
phase-frequency detector (PFD) that drives a charge pump
(CP). The charge pump incorporates fast-locking logic,
described below. Based on system requirements, the user
supplies an external loop filter and one or more VCOs. A high
speed analog mixer is included for translation synthesis loops.
Using the different blocks in the PLL frequency synthesizer in
conjunction with the DDS, the user can create translation loops
(also known as offset loops), fractional divider loops, as well as
traditional PLL loops to multiply the output of the DDS in
frequency.
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PDF描述 |
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| AD9859 | 400 MSPS, 10-Bit, 1.8 V CMOS Direct Digital Synthesizer |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD9858PCB | 制造商:AD 制造商全稱:Analog Devices 功能描述:1 GSPS Direct Digital Synthesizer |
| AD9858TLPCB | 制造商:AD 制造商全稱:Analog Devices 功能描述:1 GSPS Direct Digital Synthesizer |
| AD9858XSV | 制造商:Analog Devices 功能描述: |
| AD9859 | 制造商:AD 制造商全稱:Analog Devices 功能描述:400 MSPS, 10-Bit, 1.8 V CMOS Direct Digital Synthesizer |
| AD9859/PCB | 制造商:Analog Devices 功能描述:NCO, 400MSPS 10 BIT, 1.8V CMOS DIRECT DGTL SYNTHESIZER - Bulk |
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