MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

1

REV 2

1/98

Dual 3.3V PLL Clock Generator

The MPC980 is a 3.3V dual PLL clock generator targeted for high end

Pentium

™ and PowerPC™ 603/604 personal computers. The MPC980

synthesizes processor as well as PCI clocks from a 14.31818MHz

external crystal. In addition the device provides two buffered outputs of

the 14.31818MHz crystal as well as a 40MHz SCSI clock, a 24MHz floppy

clock and a 12MHz keyboard clock. One of the buffered 14.31818MHz

outputs can be configured to provide a 16MHz output rather than the

second copy of the 14.31818MHz output.

Designs

The processor clock outputs of the MPC980 can be programmed to

provide 50, 60 or 66MHz. Under all processor output frequencies the PCI

clock outputs will be equal to one half the processor clock outputs. The

PCI outputs will run synchronously to the processor clock outputs. There

are a total of ten output clocks which can be split into a group of four and a

group of six. Either group can be configured as processor or PCI clocks.

Each of the outputs can drive two series terminated transmission lines

allowing for the driving of up to twelve independent processor loads and

eight PCI clock loads. A pin selectable option is available to delay the PCI

clock outputs relative to the processor clocks. The amount of delay is a

function of the processor clock frequency and varies from 2ns to 6ns.

The output jitter of the the PLL at 66MHz output is

±150ps peak–to–peak, cycle–to–cycle (the worst case deviation of the clock

period is guaranteed to be less than

±150ps). The skews between one processor clock and any other processor clock (or one

PCI clock to any other PCI clock) is 350ps. The worst case skew between the processor clocks and the PCI clocks is 500ps.

An output enable pin is provided to tristate all of the outputs for board level test. In addition a testing mode is provided to allow

for the bypass of the PLL’s for board level functional debug.

Pentium is a trademark of Intel Corporation. PowerPC is a trademark of International Business

Machines Corporation.

MPC980

DUAL 3.3V PLL

CLOCK GENERATOR

FA SUFFIX

52–LEAD LQFP PACKAGE

CASE 848D–03