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## MC12429 データシート(PDF) 4 Page - Motorola, Inc

 部品番号. MC12429 部品情報 HIGH FREQUENCY CLOCK SYNTHESIZER ダウンロード 12 Pages Scroll/Zoom 100% メーカー MOTOROLA [Motorola, Inc] ホームページ http://www.freescale.com Logo ## MC12429 Datasheet(HTML) 4 Page - Motorola, Inc

 4 / 12 page MC12429MOTOROLATIMING SOLUTIONS49–BIT SR2–BIT SR3–BIT SRDIV 16Figure 3. MC12429 Block Diagram (28–Lead PLCC Pinout)16MHzS_LOADP_LOADS_DATAS_CLOCKXTAL1XTAL2OSC45PHASEDETECTOR2879–BIT DIV MCOUNTERLATCHVCODIV N(1, 2, 4, 8)LATCH200–400MHzFOUTFOUT+3.3 or 5.0V252423VCC0LATCHTEST20+3.3 or 5.0VPLL_VCC1MHzFREF01272601VCC1+3.3 or 5.0VM[8:0]9816N[1:0]217, 182122, 19OE6PROGRAMMING INTERFACEProgramming the device amounts to properly configuringthe internal dividers to produce the desired frequency at theoutputs. The output frequency can by represented by thisformula:FOUT = (FXTAL ÷ 16) x M ÷ N(1)Where FXTAL is the crystal frequency, M is the loop dividermodulus, and N is the output divider modulus. Note that it ispossible to select values of M such that the PLL is unable toachieve loop lock. To avoid this, always make sure that M isselected to be 200≤ M ≤ 400 for a 16MHz input reference.Assuming that a 16MHz reference frequency is used theabove equation reduces to:FOUT = M÷ NSubstituting the four values for N (1, 2, 4, 8) yields:TABLE A: Output Frequency RangeNFOUTOUTPUT FREQUENCY RANGE1248MM / 2M / 4M / 8200 – 400 MHZ100 – 200 MHZ50 – 100 MHZ25 – 50 MHZFrom these ranges the user will establish the value of Nrequired, then the value of M can be calculated based on theappropriate equation above. For example if an outputfrequency of 131MHz was desired the following steps wouldbe taken to identify the appropriate M and N values. 131MHzfalls within the frequency range set by an N value of 2 so N[1:0] = 01. For N = 2 FOUT = M÷ 2 and M = 2 x FOUT.Therefore M = 131 x 2 = 262, so M[8:0] = 100000110.Following this same procedure a user can generate anywhole frequency desired between 25 and 400MHz. Note thatfor N > 2 fractional values of FOUT can be realized. The sizeof the programmable frequency steps (and thus the indicatorof the fractional output frequencies acheivable) will be equalto FXTAL÷ 16 ÷ N.For input reference frequencies other than 16MHz the setof appropriate equations can be deduced from equation 1.For computer applications another useful frequency basewould be 16.666MHz. From this reference one can generatea family of output frequencies at multiples of the 33.333MHzPCI clock. As an example to generate a 133.333MHz clockfrom a 16.666MHz reference the following M and N valueswould be used:FOUT = 16.666÷ 16 x M ÷ N = 1.0416 x M ÷ N

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