參數(shù)資料
型號： 514BBAXXXXXXAAG
廠商： SILICON LABORATORIES
元件分類： 時鐘產(chǎn)生/分配
英文描述： 250 MHz, OTHER CLOCK GENERATOR, PDSO6
封裝： 5 X 7 MM, ROHS COMPILANT PACKAGE-6
文件頁數(shù)： 7/32頁
文件大?。?/td> 267K
代理商： 514BBAXXXXXXAAG
Si514
Preliminary Rev. 0.9
15
3. All-Digital PLL Applications
The Si514 uses a high resolution divider M that enables fine frequency adjustments with resolution better than
0.026 parts per billion. Fine frequency adjustments are useful when making frequency corrections that compensate
for changing ambient conditions, long term aging or when locking the Si514 to an input clock reference. Figure 3
shows a typical implementation using a system IC such as an FPGA to control the output of the Si514 in a phase-
locked application. Refer to “AN575: An Introduction to FPGA-Based ADPLLs” for more information.
Figure 3. All-Digital PLL Application Using Si514 with Dual CMOS Output
Since small frequency changes must be within ±1000 ppm of the center frequency, HS_DIV and LS_DIV remain
constant. The below expression can be used to calculate a new M2 divider value based on a desired output
frequency shift, where FOUT is in ppm.
Some systems, particularly those that use feedback control, can simplify the computation by implementing an
approximate frequency change based on toggling a bit position or adding/subtracting a bit to the existing M_Frac
value. Since M ranges approximately ±10% between 65.04065041 and 78.17385866, the effect of changing
M_Frac by a single bit depends only slightly on the absolute value of M.
For M=71 near the midpoint of the range, toggling M_Frac[0] changes the output frequency by 0.026 ppb. Each
higher order bit doubles the influence such that toggling M_Frac[1] is 0.052 ppb, M_Frac[2] is 0.1 ppb, etc. Figure 4
shows this trend across multiple registers generalized to M_Frac[N]. Coarse changes greater than ±1.7 ppm are
possible but most applications require finer transitions. Toggling each bit involves incrementing or decrementing
the bit position. Writing M_Int[8:3] in register 9 completes the operation.
Figure 4. Output Frequency Change When Toggling M_Frac[N], M=71
I2C Control
Any Frequency
DSPLL
CLK_OUT
FB
Si514
FPGA
÷
I2C
Master
Command
Conversion
Loop
Filter
PD
÷
SCL
SDA
Fin
M2
M1 1 FOUT 10
6
–
–
=
M_Int[8:0] = 000100111
M = 71.000000000000
M_Frac[28:0] = 00000000000000000000000000000
M_Frac[23:16] = 00000000
M_Frac[15:8] = 00000000
M_Frac[7:0] = 00000000
0.026ppb
6.7ppb
1.7ppm
相關PDF資料
PDF描述
514HBAXXXXXXBAG 250 MHz, OTHER CLOCK GENERATOR, PDSO6
514HBBXXXXXXBAG 170 MHz, OTHER CLOCK GENERATOR, PDSO6
514HBCXXXXXXBAGR 125 MHz, OTHER CLOCK GENERATOR, PDSO6
514HCBXXXXXXAAG 170 MHz, OTHER CLOCK GENERATOR, PDSO6
514HCBXXXXXXBAG 170 MHz, OTHER CLOCK GENERATOR, PDSO6
相關代理商/技術參數(shù)
參數(shù)描述
514BBB001011BAG 制造商:Silicon Laboratories Inc 功能描述:OSCILLATOR - Trays
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514BCA000107AAG 功能描述:可編程振蕩器 PROGRMABLE XO 6 PIN 0.7PS RS JTR RoHS:否 制造商:IDT 封裝 / 箱體:5 mm x 7 mm x 1.5 mm 頻率:15.476 MHz to 866.67, 975 MHz to 1300 MHz 頻率穩(wěn)定性:+/- 50 PPM 電源電壓:3.63 V 負載電容:10 pF 端接類型:SMD/SMT 輸出格式:LVPECL 最小工作溫度:- 40 C 最大工作溫度:+ 85 C 尺寸:7 mm W x 5 mm L x 1.5 mm H 封裝:
514BCA000107AAGR 制造商:Silicon Laboratories Inc 功能描述:OSCILLATOR - Tape and Reel
514BCA000776AAG 制造商:Silicon Laboratories Inc 功能描述:OSCILLATOR - Trays
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