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參數資料
| 型號： | LMX2531 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | PLLatinum High Performance Frequency Synthesizer System with Integrated VCO |
| 中文描述： | PLLatinum高性能頻率合成器系統的集成VCO |
| 文件頁數： | 17/25頁 |
| 文件大小： | 589K |
| 代理商： | LMX2531 |
2.0 General Programming Information
(Continued)
2.4 REGISTER R3
2.4.1 DEN[21:12] -- Extension for the Fractional Denominator
These are the MSB bits of the fractional denominator (DEN word), which have already been discussed.
2.4.2 FoLD[3:0] -- Multiplexed Output for Ftest/LD Pin
The FoLD[3:0] word is used to program the output of the FoLD Pin in accordance with the table below:
FoLD
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Output Type
High Impedance
Push-Pull
Push-Pull
Push-Pull
N/A
Push-Pull
Open-Drain
Push-Pull
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
Function
Disabled
Logical "High" State
Logical "Low" State
Digital Lock Detect
Reserved
RF N Counter divided by 2
Analog Lock Detect
Analog Lock Detect
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
2.4.3 ORDER -- Order of Delta Sigma Modulator
This bit determines the order of the delta sigma modulator in the PLL. In general, higher order fractional modulators tend to
reduce the primary fractional spurs that occur at increments of the channel spacing, but can also create spurs that are at a fraction
of the channel spacing, if there is not sufficient filtering. The optimal choice of modulator order is very application specific,
however, a third order modulator is a good starting point if not sure what to try first.
ORDER
0
Delta Sigma Modulator Order
Fourth
Reset Modulator
(Integer Mode -- all fractions are ignored)
Second
Third
1
2
3
2.4.4 DITHER -- Dithering
Dithering is useful in reducing fractional spurs, especially those that occur a a fraction of the channel spacing. The only exception
is when the fractional numerator is zero. In this case, dithering usually is not a benefit. Dithering also can sometimes increase the
PLL phase noise by a fraction of a dB. In general, if dithering is disabled, phase noise may be slightly better inside the loop
bandwidth of the system, but spurs are likely to be worse too.
DITHER
0
1
2
3
Dithering Mode
Weak Dithering
Reserved
Strong Dithering
Dithering Disabled
2.4.5 FDM -- Fractional Denominator Mode
When this bit is set to 1, the 10 MSB bits for the fractional numerator and denominator are considered. Otherwise they are
ignored. When this bit is disabled, the current consumption is about 0.5 mA lower.
L
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相關代理商/技術參數 |
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| LMX2531_07 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:High Performance Frequency Synthesizer System with Integrated VCO |
| LMX25311146EVAL | 功能描述:時鐘和定時器開發工具 LMX2531LQ1146 EVAL BOARD RoHS:否 制造商:Texas Instruments 產品:Evaluation Modules 類型:Clock Conditioners 工具用于評估:LMK04100B 頻率:122.8 MHz 工作電源電壓:3.3 V |
| LMX25311146EVAL/NOPB | 功能描述:射頻開發工具 LMX25311146 EVAL MOD RoHS:否 制造商:Taiyo Yuden 產品:Wireless Modules 類型:Wireless Audio 工具用于評估:WYSAAVDX7 頻率: 工作電源電壓:3.4 V to 5.5 V |
| LMX25311226EVAL | 功能描述:時鐘和定時器開發工具 LMX2531LQ1226 EVAL BOARD RoHS:否 制造商:Texas Instruments 產品:Evaluation Modules 類型:Clock Conditioners 工具用于評估:LMK04100B 頻率:122.8 MHz 工作電源電壓:3.3 V |
| LMX25311226EVAL/NOPB | 功能描述:射頻開發工具 LMX25311226 EVAL MOD RoHS:否 制造商:Taiyo Yuden 產品:Wireless Modules 類型:Wireless Audio 工具用于評估:WYSAAVDX7 頻率: 工作電源電壓:3.4 V to 5.5 V |
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