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SY87739LHI Datasheet(PDF) 9 Page - Micrel Semiconductor |
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SY87739LHI Datasheet(HTML) 9 Page - Micrel Semiconductor |
9 / 13 page 9 SY87739L Micrel, Inc. M9999-111406 hbwhelp@micrel.com or (408) 955-1690 NdivSel2 NdivSel1 NdivSel0 Divisor 000 16 001 16 010 18 011 17 100 31 101 14 110 32 111 15 Table 4. NdivSel Divisor Control P Divider The output of the wrapper synthesizer is post divided down before appearing at the CLKOUT± pins. Notice that, given the range of the wrapper VCO (540MHz to 729MHz) and the maximum and minimum division ratios of the P divider (1 to 60, as shown in Table 5), the minimum and maximum frequency of CLKOUT± is 10MHz and 729MHz respectively. PostDivSel Bit 43210 Divisor 00000 1 00001 3 00010 2 00011 3 00100 4 00101 5 00110 6 00111 7 01000 8 01001 9 01010 10 01011 11 01100 12 01101 13 01110 14 01111 15 10000 16 10001 18 10010 20 10011 22 10100 24 10101 26 10110 28 10111 30 11000 32 11001 36 11010 40 11011 44 11100 48 11101 52 11110 56 11111 60 Table 5. Setting to Program the Division Ratio of the P Divider The divisor value is selected via MicroWire™. The 5-bit PostDivSel register determines the divisor value. It is set as per Table 5. The SY87739L does not guarantee a 50% duty cycle output. It is designed to provide well timed rising edges only. MicroWire™ Interface This standard bit-serial interface eases interfacing the SY87739L to microcontrollers. The SY87739L accepts one data bit on PROGDI per rising edge on PROGSK. The data is ignored when PROGCS is inactive low. When PROGCS is active high, bits are shifted into the SY87739L. The falling edge of PROGCS then initiates acquisition of the output frequency defined by the 32-bit program just loaded into the SY87739L. This means that, if the user wishes to re-acquire based on the same program, PROGCS needs to toggle high then low. Programming To program the SY87739L to generate a certain frequency: 1. Determine the required values of the programming parameters, as summarized in Table 6. 2. Set PROGCS active high. 3. Shift in each of the 32 bits, as per Table 6. The fields are loaded in sequence, from the first row to the last row. For each multi-bit field, the most significant bit is shifted in first. Shift the bits in through PROGDI, clocking them with PROGSK edges. 4. Set PROGCS inactive low. 5. Wait for LOCKED to assert high. Field # Bits Reference Preamble 4 always "0000" qp 5 Section: Gating the P/P-1 Divider qpm1 5 Section: Gating the P/P-1 Divider divsel 4 Table 1 mfg. 3 always "000" PostDivSel 5 Table 5 NdivSel 3 Table 4 MdivSel 3 Table 3 Table 6. Programming Sequence The SY87739L generates exact frequencies for common serial data streaming protocols. Summary programming information appears in the next section. The SY87739L also enables Micrel’s SY87721L AnyRate™ CDR to decode virtually anything within its range of operation, all from a 27.000MHz reference. Details about how to program the SY87739L in the general case, including derivation of programs for both the standard protocols and the AnyRate™ application, appear in an applications note. |
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