MC12429 Datasheet, PDF (1/12 Pages) Motorola, Inc – HIGH FREQUENCY CLOCK SYNTHESIZER

MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
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High Frequency Clock
Synthesizer
MC12429
The MC12429 is a general purpose synthesized clock source. Its
internal VCO will operate over a range of frequencies from 200 to
400MHz. 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 1, 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. The output frequency is configured using a
parallel or serial interface.
HIGH FREQUENCY PLL
CLOCK SYNTHESIZER
• 25 to 400MHz Differential PECL Outputs
• ±25ps Peak–to–Peak Output Jitter
• Fully Integrated Phase–Locked Loop
• Minimal Frequency Over–Shoot
• Synthesized Architecture
FN SUFFIX
28–LEAD PLCC PACKAGE
CASE 776–02
• Serial 3–Wire Interface
• Parallel Interface for Power–Up
• Quartz Crystal Interface
• 28–Lead PLCC and 32–Lead LQFP Packages
• Operates from 3.3V or 5.0V Power Supply
Functional Description
FA SUFFIX
32–LEAD LQFP PACKAGE
CASE 873A–02
The internal oscillator uses the external quartz crystal as the basis of
its frequency reference. The output of the reference oscillator is divided
by 16 before being sent to the phase detector. With a 16MHz crystal, this
provides a reference frequency of 1MHz. Although this data sheet
illustrates functionality only for a 16MHz crystal, any crystal in the
10–25MHz range can be used.
The VCO within the PLL operates over a range of 200 to 400MHz. Its output is scaled by a divider that is configured by either
the serial or parallel interfaces. The output of this loop divider is also 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 50Ω to VCC – 2.0V. 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.
06/01
© Motorola, Inc. 2001
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