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MC12430 Scheda tecnica(PDF) 1 Page - Motorola, Inc |
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MC12430 Scheda tecnica(HTML) 1 Page - Motorola, Inc |
1 / 12 page MOTOROLA SEMICONDUCTOR TECHNICAL DATA 1 REV 1 © Motorola, Inc. 1997 2/97 High Frequency Clock Generator The MC12430 is a general purpose synthesized clock source targeting applications that require both serial and parallel interfaces. Its internal VCO will operate over a range of frequencies from 400 to 800MHz. The differential PECL output can be configured to be the VCO frequency divided by 1, 2, 4 or 8. With the output configured to divide the VCO frequency by 2, and with a 16.000MHz external quartz crystal used to provide the reference frequency, the output frequency can be specified in 1MHz steps. The PLL loop filter is fully integrated so that no external components are required. • 50 to 800MHz Differential PECL Outputs • ±25ps Peak–to–Peak Output Jitter • Fully Integrated Phase–Locked Loop • Minimal Frequency Over–Shoot • Synthesized Architecture • Serial 3–Wire Interface • Parallel Interface for Power–Up • Quartz Crystal Interface • 28–Lead PLCC Package • Operates from 3.3V or 5.0V Power Supply Functional Description The internal oscillator uses the external quartz crystal as the basis of its frequency reference. The output of the reference oscillator is divided by 8 before being sent to the phase detector. With a 16MHz crystal, this provides a reference frequency of 2MHz. Although this data sheet illustrates functionality only for a 16MHz crystal, any crystal in the 10–20MHz range can be used. The VCO within the PLL operates over a range of 400 to 800MHz. Its output is scaled by a divider that is configured by either the serial or parallel interfaces. The output of this loop divider is applied to the phase detector. The phase detector and loop filter attempt to force the VCO output frequency to be M times the reference frequency by adjusting the VCO control voltage. Note that for some values of M (either too high or too low) the PLL will not achieve loop lock. The output of the VCO is also passed through an output divider before being sent to the PECL output driver. This output divider (N divider) is configured through either the serial or the parallel interfaces, and can provide one of four division ratios (1, 2, 4 or 8). This divider extends performance of the part while providing a 50% duty cycle. The output driver is driven differentially from the output divider, and is capable of driving a pair of transmission lines terminated in 50 Ω to VCC – 2.0. The positive reference for the output driver and the internal logic is separated from the power supply for the phase–locked loop to minimize noise induced jitter. The configuration logic has two sections: serial and parallel. The parallel interface uses the values at the M[8:0] and N[1:0] inputs to configure the internal counters. Normally, on system reset, the P_LOAD input is held LOW until sometime after power becomes valid. On the LOW–to–HIGH transition of P_LOAD, the parallel inputs are captured. The parallel interface has priority over the serial interface. Internal pullup resistors are provided on the M[8:0] and N[1:0] inputs to reduce component count in the application of the chip. The serial interface centers on a fourteen bit shift register. The shift register shifts once per rising edge of the S_CLOCK input. The serial input S_DATA must meet setup and hold timing as specified in the AC Characteristics section of this document. The configuration latches will capture the value of the shift register on the HIGH–to–LOW edge of the S_LOAD input. See the programming section for more information. The TEST output reflects various internal node values, and is controlled by the T[2:0] bits in the serial data stream. See the programming section for more information. MC12430 HIGH FREQUENCY PLL CLOCK GENERATOR FN SUFFIX 28–LEAD PLCC PACKAGE CASE 776–02 FA SUFFIX 32–LEAD TQFP PACKAGE CASE 873A–02 |
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Descrizione simile - MC12430 |
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