鈥?/div>
卤100ps
Typical Cycle鈥搕o鈥揅ycle Jitter
FA SUFFIX
32鈥揕EAD TQFP PACKAGE
CASE 873A鈥?2
Two selectable feedback division ratios are available on the MPC950
to provide input reference clock flexibility. The FBSEL pin will choose
between a divide by 8 or a divide by 16 of the VCO frequency to be
compared with the input reference to the MPC950. The internal VCO is
running at either 2x or 4x the high speed output, depending on
configuration, so that the input reference will be either one half, one fourth
or one eighth the high speed output.
The MPC951 replaces the crystal oscillator and internal feedback of the MPC950 with a differential PECL reference input and
an external feedback input. These features allow for the MPC951 to be used as a zero delay, low skew fanout buffer. In addition,
the external feedback allows for a wider variety of input鈥搕o鈥搊utput frequency relationships. The MPC951 REF_SEL pin allows for
the selection of an alternate LVCMOS input clock to be used as a test clock or to provide the reference for the PLL from an
LVCMOS source.
The MPC950 provides an external test clock input for scan clock distribution or system diagnostics. In addition the REF_SEL
pin allows the user to select between a crystal input to an on鈥揵oard oscillator for the reference or to chose a TTL level oscillator
input directly. The on鈥揵oard crystal oscillator requires no external components beyond a series resonant crystal.
Both the MPC950 and MPC951 are fully 3.3V compatible and require no external loop filter components. All inputs accept
LVCMOS or LVTTL compatible levels while the outputs provide LVCMOS levels with the capability to drive terminated 50鈩?/div>
transmission lines. Select inputs do not have internal pull鈥搖p/pull鈥揹own resistors and thus must be set externally. If the
PECL_CLK inputs are not used, they can be left open. For series terminated 50鈩?lines, each of the MPC950/951 outputs can
drive two traces giving the device an effective fanout of 1:18. The device is packaged in a 7x7mm 32鈥搇ead TQFP package to
provide the optimum combination of board density and performance.
PowerPC is a trademark of International Business Machines Corporation. Pentium is a trademark of Intel Corporation.
2/97
漏
Motorola, Inc. 1997
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