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ADF4360-3 Fiches technique(PDF) 10 Page - Analog Devices |
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ADF4360-3 Fiches technique(HTML) 10 Page - Analog Devices |
10 / 24 page ADF4360-3 Data Sheet Rev. C | Page 10 of 24 MUXOUT AND LOCK DETECT The output multiplexer on the ADF4360 family allows the user to access various internal points on the chip. The state of MUXOUT is controlled by M3, M2, and M1 in the function latch. The full truth table is shown on Table 7. Figure 13 shows the MUXOUT section in block diagram form. Lock Detect MUXOUT can be programmed for two types of lock detect: digital and analog. Digital lock detect is active high. When LDP in the R counter latch is set to 0, digital lock detect is set high when the phase error on three consecutive phase detector cycles is less than 15 ns. With LDP set to 1, five consecutive cycles of less than 15 ns phase error are required to set the lock detect. It will stay set high until a phase error of greater than 25 ns is detected on any subsequent PD cycle. The N-channel open-drain analog lock detect should be operated with an external pull-up resistor of 10 kΩ nominal. When lock has been detected, this output will be high with narrow low-going pulses. R COUNTER OUTPUT N COUNTER OUTPUT DIGITAL LOCK DETECT DGND CONTROL MUX MUXOUT DVDD ANALOG LOCK DETECT SDOUT Figure 13. MUXOUT Circuit INPUT SHIFT REGISTER The ADF4360 family’s digital section includes a 24-bit input shift register, a 14-bit R counter, and an 18-bit N counter, comprised of a 5-bit A counter and a 13-bit B counter. Data is clocked into the 24-bit shift register on each rising edge of CLK. The data is clocked in MSB first. Data is transferred from the shift register to one of four latches on the rising edge of LE. The destination latch is determined by the state of the two control bits (C2, C1) in the shift register. These are the two LSBs—DB1, DB0—as shown in Figure 2. The truth table for these bits is shown in Table 5. Table 6 shows a summary of how the latches are programmed. Note that the test mode latch is used for factory testing and should not be programmed by the user. Table 5. C2 and C1 Truth Table Control Bits C2 C1 Data Latch 0 0 Control Latch 0 1 R Counter 1 0 N Counter (A and B) 1 1 Test Mode Latch VCO The VCO core in the ADF4360 family uses eight overlapping bands, as shown in Figure 14, to allow a wide frequency range to be covered without a large VCO sensitivity (KV) and resultant poor phase noise and spurious performance. The correct band is chosen automatically by the band select logic at power-up or whenever the N counter latch is updated. It is important that the correct write sequence be followed at power-up. This sequence is 1. R counter latch 2. Control latch 3. N counter latch During band select logic, which takes five PFD cycles, the VCO VTUNE is disconnected from the output of the loop filter and connected to an internal reference voltage. 0.7 0.5 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.7 2.5 2.3 2.9 3.1 3.3 2050 1950 1850 1750 1650 1550 1450 1350 FREQUENCY (MHz) Figure 14. Frequency vs. VTUNE, ADF4360-3 The R counter output is used as the clock for the band select logic and should not exceed 1 MHz. A programmable divider is provided at the R counter input to allow division by 1, 2, 4, or 8 and is controlled by Bits BSC1 and BSC2 in the R counter latch. Where the required PFD frequency exceeds 1 MHz, the divide ratio should be set to allow enough time for correct band selection. After band select, normal PLL action resumes. The nominal value of KV is 45 MHz/V or 23 MHz/V if divide-by-2 operation has been selected (by programming DIV2 [DB22] high in the N counter latch). The ADF4360 family contains linearization circuitry to minimize any variation of the product of ICP and KV. |
Numéro de pièce similaire - ADF4360-3 |
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Description similaire - ADF4360-3 |
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