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參數(shù)資料
| 型號： | TRF2050PW |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | PLL合成/DDS/VCOs |
| 英文描述： | PLL FREQUENCY SYNTHESIZER, 1200 MHz, PDSO20 |
| 封裝： | PLASTIC, SO-20 |
| 文件頁數(shù)： | 18/34頁 |
| 文件大?。?/td> | 543K |
| 代理商： | TRF2050PW |
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TRF2050
LOW-VOLTAGE 1.2-GHz FRACTIONAL-N/INTEGER-N SYNTHESIZER
SLWS030E– JUNE 1996 – REVISED OCTOBER 2000
25
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
PRINCIPLES OF OPERATION
main divider – fractional-N sidebands and compensation
Programming a fractional-N channel means the main divider and prescaler divide by N or N + 1 as dictated by
the operation of the fractional accumulator. Because the main divider operation is integer in nature and the
desired VCO frequency is not, the output of the main phase detector is modulated with a resultant fractional-N
phase ripple that produces sideband energy if left uncompensated. This phase ripple is proportional and
synchronized to the contents of the fractional accumulator that is used to control fractional-N sideband
compensation. Only channels that require a nonzero value of NF have the fractional-N sideband energy. The
fractional-N sidebands, which appear at offset frequencies from the VCO fundamental tone, are multiples of
NF/FMOD. Figure 22 shows the fractional-N phase detector ripple for a 3/8 fractional channel.
240 kHz
03
6
1
4
7
2
5
0
Main Phase
Detector Reference
Main Phase
Detector VCO
Feedback
Main Phase
Detector Fractional-N
Ripple
Fractional
Accumulator State
Figure 22. Fractional-N Phase Detector Ripple for 3/8 Channel
The TRF2050 has internal circuitry that provides a means to compensate for the phase detector fractional-N
phase ripple, thereby significantly reducing the magnitude of the fractional-N sidebands. Because the current
waveform output of the main PLL proportional charge pumps is modulated with the phase detector fractional-N
phase ripple, a fractional-N compensation charge-pump output is summed with the main PLL proportional
charge pump.
Figure 23 shows the fractional-N ripple magnitude on the main PHP charge-pump output. The magnitude is
essentially constant, and the pulse width is modulated with the contents of the fractional accumulator. The area
under the main PHP charge-pump curve represents the amount of charge delivered to the loop filter network.
In order to minimize fractional-N sidebands in the VCO spectrum, the compensation current waveform is
generated to have
equal and opposite sign magnitude area to the main PHP charge pump.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| TRF2052 | 制造商:TI 制造商全稱:Texas Instruments 功能描述:LOW-VOLTAGE 2-GHz SYNTHESIZER |
| TRF2052PW | 功能描述:IC LV 2-GHZ SYNTH 20-TSSOP RoHS:否 類別:集成電路 (IC) >> 時鐘/計時 - 時鐘發(fā)生器，PLL，頻率合成器 系列:- 標準包裝:2,000 系列:- 類型:PLL 頻率合成器 PLL:是 輸入:晶體 輸出:時鐘 電路數(shù):1 比率 - 輸入:輸出:1:1 差分 - 輸入:輸出:無/無 頻率 - 最大:1GHz 除法器/乘法器:是/無 電源電壓:4.5 V ~ 5.5 V 工作溫度:-20°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:16-LSSOP（0.175"，4.40mm 寬） 供應商設備封裝:16-SSOP 包裝:帶卷 (TR) 其它名稱:NJW1504V-TE1-NDNJW1504V-TE1TR |
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| TRF2056PW | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| TRF2253PWR | 制造商:Texas Instruments 功能描述: |
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