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參數資料
| 型號： | AD9858 |
| 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的直接數字頻率合成器 |
| 文件頁數： | 28/32頁 |
| 文件大小： | 1412K |
| 代理商： | AD9858 |
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AD9858
Phase Offset Control
Rev. A | Page 28 of 32
A 14-bit phase offset (θ) may be added to the output of the
phase accumulator by means of the phase offset words stored in
the memory registers. This feature provides the user with three
different methods of phase control.
The first method is a static phase adjustment, where a fixed
phase offset is loaded into the appropriate phase-offset register
and left unchanged. The result is that the output signal is offset
by a constant angle relative to the nominal signal. This allows
the user to phase align the DDS output with an external signal,
if necessary.
The second method of phase control is where the user regularly
updates the appropriate phase-offset register via the I/O port.
By properly modifying the phase offset as a function of time,
the user can implement a phase modulated output signal. The
rate at which phase modulation can be performed is limited by
both the speed of the I/O port and the frequency of SYSCLK.
The third method of phase control involves the profile registers,
in which the user loads up to four different phase-offset values
into the appropriate profiles. The user can then select among
the four preloaded phase-offset values via the AD9858 profile
select pins. Thus, the phase changes are accomplished by driving
the hardware pins rather than writing to the I/O port, thereby
avoiding the speed limitation imposed by the I/O port.
However, this method is restricted to only four phase-offset
values (one phase-offset value per profile). Each profile has an
associated frequency and phase value. Changing the current
profile updates both parameters, so care must be taken to
ensure that no unwanted parameter changes take place.
Note that the phase-offset value is routed through a unit delay
(z
–1
) block. This is done to ensure that updates of the phase-
offset values exhibit the same amount of latency as updates of
the frequency tuning word. Otherwise, if the user decides to
update both frequency and phase-offset values, the phase-offset
change would propagate through the device before the tuning
word change. The presence of the unit delay in the phase-offset
path ensures that both frequency and phase-offset changes
exhibit similar latency.
Profile Selection
A profile consists of a specific group of memory registers (see
Table 6). In the AD9858 each profile contains a 32-bit frequency
tuning word and a 14-bit phase-offset word. Each profile is
selectable via two external profile select pins (PS0 and PS1) as
defined in Table 12. The specific mapping of registers to profiles
is detailed in the Register Bit Descriptions section. The user
should be aware that selection of a profile is internally
synchronized with DDS CLK using the SYNCLK timing. That
is, SYNCLK is used to synchronize the assertion of the profile
select pins (PS0, PS1). Therefore, the PS0 and PS1 pins must be
set up and held around the rising edge of SYNCLK. The PS0
and PS1 inputs are designed for zero hold time and 3.5 ns
setup time.
Table 12.
PS1
PS0
0
0
0
1
1
0
1
1
Profile
0
1
2
3
The profiles are available to the user to provide rapid changing
of device parameters via external hardware, which alleviates the
speed limitations imposed by the I/O port. For example, the
user might preprogram the four phase offset registers with
values that correspond to phase increments of 90°. By
controlling the PS0 and PS1 pins, the user can implement
π
/2
phase modulation. The data modulation rate would be much
higher than that possible by repeatedly reloading a single phase-
offset register via the I/O port.
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相關代理商/技術參數 |
參數描述 |
|---|---|
| AD9858/FDPCB | 制造商:Analog Devices 功能描述:EVAL KIT FOR FRACTIONAL DIVIDER EVAL BD - Bulk |
| AD9858/PCBZ | 功能描述:BOARD EVAL FOR AD9858 RoHS:是 類別:編程器，開發系統 >> 評估演示板和套件 系列:- 標準包裝:1 系列:PSoC® 主要目的:電源管理，熱管理 嵌入式:- 已用 IC / 零件:- 主要屬性:- 次要屬性:- 已供物品:板，CD，電源 |
| AD9858/TLPCB | 制造商:Analog Devices 功能描述:NCO/DDS, 1GSPS DIRECT DGTL SYNTHESIZER - Bulk |
| AD9858/TLPCBZ | 制造商:Analog Devices 功能描述:EVAL BOARD - Bulk |
| AD9858BSV | 制造商:Rochester Electronics LLC 功能描述:1000 MHZ DDS/DAC - Bulk 制造商:Analog Devices 功能描述:1GHZ DDS/DAC SMD 9858 TQFP100 制造商:Analog Devices 功能描述:Frequency Synthesizer,AD9858 1GHz TQFP |
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