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參數資料
| 型號： | ADF4154 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | XO, clock |
| 英文描述： | Fractional-N Frequency Synthesizer |
| 中文描述： | 分數N頻率合成器 |
| 文件頁數： | 18/20頁 |
| 文件大小： | 470K |
| 代理商： | ADF4154 |
ADF4154
If fast-lock is not used, then use the following sequence:
Rev. 0 | Page 18 of 20
1.
Load the
noise and spur register
.
2.
Load the
control register
.
3.
Load the
R-divider register
with DB23 = 0 and other
necessary parameters.
4.
Load the
N-divider register
,
including fast-lock = 0
(DB23) for normal operation.
To change frequency, only Step 4 need be repeated.
FAST-LOCK: A WORKED EXAMPLE
Consider an example in which PLL has reference frequencies of
13 MHz and F
PFD
= 13 MHz and a required lock time of 50 μs.
Therefore, the PLL is set to wide bandwidth for 40 μs.
If the time period chosen for the wide bandwidth is 40 μs, then
Fast-lock timer value = time in wide bandwidth ×
F
PFD
Fast-lock timer value = 40 μs × 13 MHz = 520
Therefore, 520 has to be loaded into the R-divider register in
Step 1 of the sequence described in the Fast-Lock Timer and
Register Sequences section.
FAST-LOCK: LOOP FILTER TOPOLOGY
To use fast-lock mode, an extra connection from the PLL to the
loop filter is needed. The MUXOUT must reduce the damping
resistor in the loop filter to while in wide bandwidth mode.
This is required because the charge pump current is increased
by 16 while in wide bandwidth mode and stability must be
ensured. This can be done with the following two topologies:
1.
Divide the damping resistor (R1) into two values (R1 and
R1A) of ratio 1:3 (see Figure 22).
2.
Use an extra resistor (R1A) and connect it directly from the
MUXOUT, as shown in Figure 22. The extra resistor must
be chosen such that the parallel combination of an extra
resistor and the damping resistor (R1) is reduced to of
the original value of R1 alone (see Figure 23).
ADF4154
CP
MUXOUT
C1
C2
R2
R1
R1A
C3
VCO
0
Figure 22 Fast-lock Loop Filter Topology—Topology 1
ADF4154
CP
MUXOUT
C1
C2
R2
R1
R1A
C3
VCO
0
Figure 23. Fast-lock Loop Filter Topology—Topology 2
SPURIOUS SIGNALS
Predicting Where They Appear
As in integer-N PLLs, spurs appear at PFD frequency offsets
from the carrier. In a fractional-N PLL, spurs also appear at
frequencies equal to the RF
OUT
channel step resolution (f
RES
).
The third-order fractional interpolator engine of the ADF4154
may also introduce subfractional spurs. If the fractional deno-
minator (MOD) is divisible by 2, spurs appear at f
RES.
If the
fractional denominator (MOD) is divisible by 3, spurs appear at
1/3 f
RES.
Harmonics of all spurs mentioned also appear. With the
lowest spur mode enabled, the fractional and subfractional
spurs are attenuated dramatically. The worst-case spurs appear
when the fraction is programmed to 1/MOD. For example, in a
GSM 900 MHz system with a 26 MHz PFD frequency and an
RF
OUT
channel step resolution (f
RES
) of 200 kHz, the MOD = 130.
PFD spurs appear at 26 MHz offset and fractional spurs appear
at 200 kHz offset. Since the MOD is divisible by 2, subfractional
spurs are also present at 100 kHz offset.
FILTER DESIGN—ADISIMPLL
A filter design and analysis program is available to help the user
implement the PLL design. Visit www.analog.com/pll for a free
download of the ADIsimPLL software. The software designs,
simulates, and analyzes the entire PLL frequency and time
domain response. Various passive and active filter architectures
are allowed. Rev. 2 of ADIsimPLL allows analysis of the
ADF4154.
INTERFACING
The ADF4154 has a simple, SPI compatible serial interface for
writing to the device. SCLK, SDATA, and LE control the data
transfer. When LE (latch enable) is high, the 22 bits that have
been clocked into the input register on each rising edge of
SCLK are transferred to the appropriate latch. See Figure 2 for
the timing diagram and Table 5 for the latch truth table.
The maximum allowable serial clock rate is 20 MHz. This
means that the maximum update rate possible for the device is
909 kHz or one update every 1.1 μs. This is more than adequate
for systems that have typical lock times in the hundreds of
microseconds.
相關PDF資料 |
PDF描述 |
|---|---|
| ADF4154BCP | Fractional-N Frequency Synthesizer |
| ADF4154BCP-REEL | Fractional-N Frequency Synthesizer |
| ADF4154BCP-REEL7 | Fractional-N Frequency Synthesizer |
| ADF4154BRU | Fractional-N Frequency Synthesizer |
| ADF4154BRU-REEL | Fractional-N Frequency Synthesizer |
相關代理商/技術參數 |
參數描述 |
|---|---|
| ADF4154BCP | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Single 20-Pin LFCSP EP 制造商:Rochester Electronics LLC 功能描述:FRACTIONAL-N SYNTH. W/FASTLOCK COUNTER - Bulk |
| ADF4154BCP-REEL | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Single 20-Pin LFCSP EP T/R 制造商:Rochester Electronics LLC 功能描述:FRACTIONAL-N SYNTH. W/FASTLOCK COUNTER - Tape and Reel |
| ADF4154BCP-REEL7 | 制造商:Analog Devices 功能描述:PLL Frequency Synthesizer Single 20-Pin LFCSP EP T/R |
| ADF4154BCPZ | 功能描述:IC FRACTION-N FREQ SYNTH 20LFCSP RoHS:是 類別:集成電路 (IC) >> 時鐘/計時 - 時鐘發生器，PLL，頻率合成器 系列:- 標準包裝:1,000 系列:Precision Edge® 類型:時鐘/頻率合成器 PLL:無 輸入:CML，PECL 輸出:CML 電路數:1 比率 - 輸入:輸出:2:1 差分 - 輸入:輸出:是/是 頻率 - 最大:10.7GHz 除法器/乘法器:無/無 電源電壓:2.375 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-VFQFN 裸露焊盤，16-MLF? 供應商設備封裝:16-MLF?（3x3） 包裝:帶卷 (TR) 其它名稱:SY58052UMGTRSY58052UMGTR-ND |
| ADF4154BCPZ-RL | 功能描述:IC FRACTION-N FREQ SYNTH 20LFCSP RoHS:是 類別:集成電路 (IC) >> 時鐘/計時 - 時鐘發生器，PLL，頻率合成器 系列:- 標準包裝:1,000 系列:Precision Edge® 類型:時鐘/頻率合成器 PLL:無 輸入:CML，PECL 輸出:CML 電路數:1 比率 - 輸入:輸出:2:1 差分 - 輸入:輸出:是/是 頻率 - 最大:10.7GHz 除法器/乘法器:無/無 電源電壓:2.375 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-VFQFN 裸露焊盤，16-MLF? 供應商設備封裝:16-MLF?（3x3） 包裝:帶卷 (TR) 其它名稱:SY58052UMGTRSY58052UMGTR-ND |
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