May 2005

ASM2I9942C

rev 0.2

Alliance Semiconductor

2575, Augustine Drive

• Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855.4999 • www.alsc.com

Notice: The information in this document is subject to change without notice.

Low Voltage 1:18 Clock Distribution Chip

Features

LVCMOS/LVTTL Clock Input

2.5V

LVCMOS

Outputs

for

Pentium

II

TM*

Microprocessor Support

150pS Maximum Targeted Output–to–Output Skew

32–Lead TQFP and LQFP Packaging

Single 3.3V or 2.5V Supply.

Pin and Function compatible to MPC942C

.

Functional Description

The ASM2I9942C is a 1:18 low voltage clock distribution

chip with 2.5V or 3.3V LVCMOS output capabilities. The

device is offered in two versions; the ASM2I9942C has an

LVCMOS input clock while the ASM2I9942P has an

LVPECL input clock. The 18 outputs are 2.5V or 3.3V

LVCMOS compatible and feature the drive strength to drive

50Ω series or parallel terminated transmission lines. With

output–to–output skews of 200pS, the ASM2I9942C is

ideal as a clock distribution chip for the most demanding of

synchronous systems. The 2.5V outputs also make the

device ideal for supplying clocks for a high performance

Pentium II

With a low output impedance (≈12Ω), in both the HIGH and

LOW logic states, the output buffers of the ASM2I9942C

are ideal for driving series terminated transmission lines.

With an output impedance of 12Ω, the ASM2I9942C can

drive two series terminated transmission lines from each

output. This capability gives the ASM2I9942C an effective

fanout of 1:36. The ASM2I9942C provides enough copies

of low skew clocks for most high performance synchronous

systems.

The LVCMOS/LVTTL input of the ASM2I9942C provides a

more standard LVCMOS interface. The OE pins will place

the outputs into a high impedance state. The OE pin has an

internal pullup resistor.

pins require either 2.5V or 3.3V. The 32–lead TQFP and

LQFP package is chosen to optimize performance, board

space and cost of the device. The 32–lead TQFP has a

7x7mm

*Pentium II is a trademark of Intel Corporation