May 2005

ASM2I99448

rev 0.3

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.

3.3V/2.5V LVCMOS 1:12 Clock Fanout Buffer

Features

12 LVCMOS compatible clock outputs

Selectable LVCMOS and differential LVPECL

compatible clock inputs

Maximum clock frequency of 350MHz

Maximum clock skew of 150pS

Synchronous output stop in logic low state

eliminates output runt pulses

High–impedance output control

3.3V or 2.5V power supply

Drives up to 24 series terminated clock lines

Ambient temperature range –40°C to +85°C

32–Lead LQFP & TQFP packaging

Supports

clock

distribution

in

networking,

telecommunication and computing applications

Pin and Function compatible to MPC9448 and

MPC948

Functional Description

The ASM2I99448 is a 3.3V or 2.5V compatible, 1:12 clock

fanout buffer targeted for high performance clock tree

applications. With output frequencies up to 350 MHz and

output skews less than 150 pS, the device meets the needs

of most demanding clock applications.

The ASM2I99448 is specifically designed to distribute

LVCMOS compatible clock signals up to a frequency of

350MHz. Each output provides a precise copy of the input

signal with a near zero skew. The outputs buffers support

driving of 50Ω terminated transmission lines on the incident

edge: each output is capable of driving either one parallel

terminated or two series terminated transmission lines.

Two selectable, independent clock inputs are available,

providing support of LVCMOS and differential LVPECL

clock distribution systems. The ASM2I99448 CLK_STOP

control is synchronous to the falling edge of the input clock.

It allows the start and stop of the output clock signal only in

a logic low state, thus eliminating potential output runt

pulses. Applying the OE control will force the outputs into

high–impedance mode.

All inputs have an internal pull–up or pull–down resistor

preventing unused and open inputs from floating. The

device supports a 2.5V or 3.3V power supply and an

ambient temperature range of –40°C to +85°C. The

ASM2I99448

is

pin

and

function

compatible

but

performance–enhanced to the MPC948.