參數(shù)資料
型號(hào): 514BBAXXXXXXAAG
廠商: SILICON LABORATORIES
元件分類: 時(shí)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(yè)數(shù): 3/32頁(yè)
文件大?。?/td> 267K
代理商: 514BBAXXXXXXAAG
Si514
Preliminary Rev. 0.9
11
e. Register 9 = 0x09 (M_Int[8:3])
f. M_Int = 0b001001010 = 0x4A = 0d74
g. M_Frac = 0x097C65D3 = 159,147,475
h. M= M_Int + M_Frac/229 = 74 + 159,147,475/229 = 74.296435272321105
2. Calculate Mnew:
a. Mnew = 74.296435272321105 x 148.352/148.5 = 74.2223889933965
b. M_Intnew = 74 = 0x4A
c. M_Fracnew = 0.2223889933965 x 229 = 119,394,181 = 0x071DCF85
3. Write Mnew to Registers 5-7:
a. Register 5 = 0x85
b. Register 6 = 0xCF
c. Register 7 = 0x1D
4. Write Mnew to Register 8:
a. Register 8 = 0x47
5. Write Mnew to Register 9:
a. Register 9 = 0x09
2.3. Programming a Large Frequency Change (> ±1000 ppm)
Large frequency changes are those that vary the FVCO frequency by an amount greater than ±1000 ppm from an
operating FCENTER. Figure 2 illustrates the difference between large and small frequency changes. Changing from
FCENTER to F'CENTER requires a calibration cycle that resets internal circuitry to establish F'CENTER as the new
operating center frequency. The below steps are recommended when performing large frequency changes:
1. Disable the output: Write OE register bit to a 0 (Register 132, bit2)
2. If using one of the standard frequencies listed in Table 9, then write the new LP1, LP2, M_Frac, M_Int, HS_DIV
and LS_DIV register values according to the table (be sure to write M_Int[8:3] (Register 9) after writing to the
M_Frac registers (Registers 5-8)). Skip to Step 9. If the desired frequency is not in the table, then follow steps
4-8 below.
3. Determine the minimum value of LS_DIV (minimizing LS_DIV minimizes the number of dividers on the output
stage, thus minimizing jitter) according to the following formula:
a. LS_DIV = FVCO(MIN)/(FOUT x HS_DIV(MAX)) (Eq 2.6)
b. LS_DIV = 2080/(FOUT(MHz) x 1022) (Eq 2.7)
i. Since LS_DIV is restricted to: dividing by 1,2,4,8,16,32, choose the next largest value over the
result derived in Eq 2.7 (e.g., if result is 4.135, choose LS_DIV = 8)
4. Determine the minimum value for HS_DIV (this optimizes timing margins)
a. HS_DIV(MIN) = FVCO(MIN)/(FOUT x LS_DIV) (Eq 2.8)
b. HS_DIV(MIN) = 2080/(FOUT(MHz) x LS_DIV) (Eq 2.9)
i.HS_DIV(MIN) will be the next even number greater than or equal to the result derived in Eq 2.9
(keeping in the range of 10-1022)
Note:
SPEED_GRADE_MIN (Reg 48) ≤ LS_DIV x HS_DIV ≤ SPEED_GRADE_MAX (Reg 49); If outside this range, the output
will be forced to the disabled state.
5. Determine a value for M according to the following formula (all values are in decimal format):
a. M = LS_DIV x HS_DIV x FOUT/FXO (Eq 2.10)
b. M = LS_DIV x HS_DIV x FOUT(MHz)/31.98 (Eq 2.11)
c. M_Int = INT[M] (Eq 2.12)
d. M_Frac = (M – INT[M]) x 229 (Eq 2.13)
相關(guān)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
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