DATA SHEET
Document Number: MC88LV926
Rev. 7, 4/2006
Freescale Semiconductor
Technical Data
MC88LV926
Low Skew CMOS PLL 68060 Clock
Low
Driver Skew CMOS PLL 68060
MC88LV926
Clock Driver
The MC88LV926 Clock Driver utilizes phase-locked loop technology to lock its
low skew outputs' frequency and phase onto an input reference clock. It is
designed to provide clock distribution for CISC microprocessor or single
processor RISC systems. The RST_IN/RST_OUT(LOCK) pins provide a
processor reset function designed specifically for the MC68/EC/LC030/040/060
microprocessor family. To support the 68060 processor, the 88LV926 operates
from a 3.3 V supply.
The PLL allows the high current, low skew outputs to lock onto a single clock
input and distribute it to multiple locations on a board. The PLL also allows the
MC88LV926 to multiply a low frequency input clock and distribute it locally at a
higher (2X) system frequency.
LOW SKEW CMOS PLL
68080 CLOCK DRIVER
Features
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2X_Q Output Meets All Requirements of the 50 and 66 MHz 68060
Microprocessor PCLK Input Specifications
Low Voltage 3.3 V VCC
Three Outputs (Q0–Q2) with Output–Output Skew <500 ps
CLKEN Output for Half Speed Bus Applications
The Phase Variation from Part-to-Part Between SYNC and the ‘Q' Outputs Is
Less than 600 ps (Derived from the TPD Specification, Which Defines the
Part-to-Part Skew)
SYNC Input Frequency Range from 5.0 MHz to 2X_Q FMax/4
All Outputs Have ± 36 mA Drive (Equal High and Low) CMOS Levels
Can Drive Either CMOS or TTL Inputs. All Inputs Are TTL-Level Compatible
with VCC = 3.3 V
Test Mode Pin (PLL_EN) Provided for Low Frequency Testing
20-Lead SOIC Pb-Free Package Available
DW SUFFIX
20-LEAD PLASTIC SOIC PACKAGE
CASE 751D-06
EG SUFFIX
20-LEAD PLASTIC SOIC PACKAGE
Pb-FREE PACKAGE
CASE 751D-06
Three ‘Q' outputs (Q0-Q2) are provided with less than 500 ps skew between their rising edges. A 2X_Q output runs at twice
the ‘Q' output frequency. The 2X_Q output is ideal for 68060 systems which require a 2X processor clock input, and it meets the
tight duty cycle spec of the 50 and 66 MHz 68060. The QCLKEN output is designed to drive the CLKEN input of the 68060 when
the bus logic runs at half of the microprocessor clock rate. The QCLKEN output is skewed relative to the 2X_Q output to ensure
that CLKEN setup and hold times of the 68060 are satisfied. A Q/2 frequency is fed back internally, providing a fixed 2X
multiplication from the ‘Q' outputs to the SYNC input. Since the feedback is done internally (no external feedback pin is provided)
the input/output frequency relationships are fixed. The Q3 output provides an inverted clock output to allow flexibility in the clock
tree design.
In normal phase-locked operation the PLL_EN pin is held high. Pulling the PLL_EN pin low disables the VCO and puts the
88LV926 in a static ‘test mode'. In this mode there is no frequency limitation on the input clock, which is necessary for a low
frequency board test environment.
The RST_OUT(LOCK) pin doubles as a phase-lock indicator. When the RST_IN pin is held high, the open drain RST_OUT
pin will be pulled actively low until phase-lock is achieved. When phase-lock occurs, the RST_OUT(LOCK) is released and a pullup resistor will pull the signal high. To give a processor reset signal, the RST_IN pin is toggled low, and the RST_OUT(LOCK)
pin will stay low for 1024 cycles of the ‘Q' output frequency after the RST_IN pin is brought back high.
Description of the RST_IN/RST_OUT(LOCK) Functionality
The RST_IN and RST_OUT(LOCK) pins provide a 68030/040/060 processor reset function, with the RST_OUT pin also acting
as a lock indicator. If the RST_IN pin is held high during system power-up, the RST_OUT pin will be in the low state until steady
state phase/frequency lock to the input reference is achieved. 1024 ‘Q' output cycles after phase-lock is achieved the
RST_OUT(LOCK) pin will go into a high impedance state, allowing it to be pulled high by an external pull-up resistor (see the AC/
DC specs for the characteristics of the RST_OUT(LOCK) pin). If the RST_IN pin is held low during power-up, the
RST_OUT(LOCK) pin will remain low.
IDT™ Low Skew CMOS PLL 68060 Clock Driver
MC88LV926
© Freescale Semiconductor, Inc., 2005. All acquired by Integrated Device Technology, Inc
Freescale Timing Solutions Organization has been rights reserved.
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