MOTOROLA

SEMICONDUCTOR TECHNICAL DATA

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Advance Information

Low Voltage 1:18 Clock

Distribution Chip

The MPC940 is a 1:18 low voltage clock distribution chip. The device

features the capability to select either a differential LVPECL or an LVTTL/

LVCMOS compatible input. The 18 outputs are LVCMOS or LVTTL

compatible and feature the drive strength to drive 50

Ω series or parallel

terminated transmission lines. With output–to–output skews of 150ps, the

MPC940 is ideal as a clock distribution chip for the most demanding of

synchronous systems. For a similar product with a larger number of

outputs, please consult the MPC941 data sheet.

With a low output impedance (

≈20Ω), in both the HIGH and LOW logic

states, the output buffers of the MPC940 are ideal for driving series

terminated transmission lines. More specifically, each of the 18 MPC940

outputs can drive two series terminated 50

Ω transmission lines. With this

capability, the MPC940 has an effective fanout of 1:36 in applications

where each line drives a single load. With this level of fanout, the

MPC940 provides enough copies of low skew clocks for most high

performance synchronous systems.

The differential LVPECL inputs of the MPC940 allow the device to interface directly with a LVPECL fanout buffer like the

MC100EP111 to build very wide clock fanout trees or to couple to a high frequency clock source. The LVCMOS/LVTTL input

provides a more standard interface for applications requiring only a single clock distribution chip at relatively low frequencies. In

addition, the two clock sources can be used to provide for a test clock interface as well as the primary system clock. A logic HIGH

on the LVCMOS_CLK_Sel pin will select the TTL level clock input.

The MPC940 is fully 3.3V compatible. The 32–lead TQFP package was chosen to optimize performance, board space and

cost of the device. The 32–lead TQFP has a 7x7mm body size with a conservative 0.8mm pin spacing.

This document contains information on a new product. Specifications and information herein are subject to

change without notice.

MPC940

LOW VOLTAGE

1:18 CLOCK

DISTRIBUTION CHIP

FA SUFFIX

32–LEAD TQFP PACKAGE

CASE 873A–02