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ICS8432DYI-101LF Datasheet(PDF) 2 Page - Integrated Circuit Systems |
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ICS8432DYI-101LF Datasheet(HTML) 2 Page - Integrated Circuit Systems |
2 / 18 page 8432DYI-101 www.icst.com/products/hiperclocks.html REV. A MAY 23, 2005 2 Integrated Circuit Systems, Inc. ICS8432I-101 700MHZ, DIFFERENTIAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER rial event occurs. As a result, the M and N bits can be hardwired to set the M divider and N output divider to a specific default state that will automatically occur during power-up. The TEST output is LOW when operating in the parallel input mode. The relationship between the VCO frequency, the input frequency and the M divider is defined as follows: The M value and the required values of M0 through M8 are shown in Table 3B, Programmable VCO Frequency Function Table. Valid M values for which the PLL will achieve lock for a 25MHz reference are defined as 8 ≤ M ≤ 28. The frequency out is defined as follows: Serial operation occurs when nP_LOAD is HIGH and S_LOAD is LOW. The shift register is loaded by sampling the S_DATA bits with the rising edge of S_CLOCK. The contents of the shift register are loaded into the M divider and N output divider when S_LOAD transitions from LOW-to-HIGH. The M divide and N out- put divide values are latched on the HIGH-to-LOW transition of S_LOAD. If S_LOAD is held HIGH, data at the S_DATA input is passed directly to the M divider and N output divider on each rising edge of S_CLOCK. The serial mode can be used to program the M and N bits and test bits T1 and T0.The internal reg- isters T0 and T1 determine the state of the TEST output as follows: Time SERIAL LOADING PARALLEL LOADING t S t H t S t H t S M, N FUNCTIONAL DESCRIPTION NOTE: The functional description that follows describes op- eration using a 25MHz clock input. Valid PLL loop divider val- ues for different input frequencies are defined in the Input Fre- quency Characteristics, Table 5, NOTE 1. The ICS8432I-101 features a fully integrated PLL and there- fore requires no external components for setting the loop band- width. A differential clock input is used as the input to the ICS8432-101. This input is fed into the phase detector. A 25MHz clock input provides a 25MHz phase detector refer- ence frequency. The VCO of the PLL operates over a range of 250MHz to 700MHz. The output of the M divider is also applied to the phase detector. The phase detector and the M divider force the VCO output frequency to be M times the reference frequency by adjust- ing the VCO control voltage. Note, that for some values of M (either too high or too low), the PLL will not achieve lock. The output of the VCO is scaled by a divider prior to being sent to each of the LVPECL output buffers. The divider provides a 50% output duty cycle. The programmable features of the ICS8432I-101 support two input modes to program the PLL M divider and N output divider. The two input operational modes are parallel and serial. Figure1 shows the timing diagram for each mode. In parallel mode, the nP_LOAD input is initially LOW. The data on inputs M0 through M8 and N0 and N1 is passed directly to the M divider and N output divider. On the LOW-to-HIGH transition of the nP_LOAD input, the data is latched and the M divider remains loaded until the next LOW transition on nP_LOAD or until a se- fVCO = f IN x M T1 T0 TEST Output 0 0 LOW 0 1 S_Data, Shift Register Input 1 0 Output of M divider 1 1 CMOS Fout FIGURE 1. PARALLEL & SERIAL LOAD OPERATIONS *NOTE: The NULL timing slot must be observed. T1 T0 *NULL N1 N 0 M8 M7 M6 M5 M4 M3 M2 M1 M0 S_CLOCK S_DATA S_LOAD nP_LOAD M0:M8, N0:N1 nP_LOAD S_LOAD fOUT = fVCO = f IN x M NN |
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