SY89843U

Precision LVPECL Runt Pulse Eliminator 2:1

MUX with 1:2 Fanout and Internal Termination

Precision Edge is a registered trademark of Micrel, Inc.

MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

March 2005

M9999-031505

General Description

The SY89843U is a low jitter PECL, 2:1 differential input

multiplexer (MUX) optimized for redundant source

switchover applications. Unlike standard multiplexers,

the SY89843U unique 2:1 Runt Pulse Eliminator (RPE)

MUX prevents any short cycles or “runt” pulses during

switchover. In addition, a unique Fail-Safe Input

protection prevents metastable conditions when the

selected input clock fails to a DC voltage (voltage

between the pins of the differential input drops below

100mV).

The differential input includes Micrel’s unique, 3-pin

input termination architecture that allows customers to

interface to any differential signal (AC- or DC-coupled)

or termination resistor networks in the signal path. The

output is 800mV, 100K compatible LVPECL with fast

rise/fall times guaranteed to be less than 190ps.

The SY89843U operates from a 2.5V ±5% or 3.3V

±10% supply and is guaranteed over the full industrial

temperature range of –40°C to +85°C. The SY89843U is

part of Micrel’s high-speed, Precision Edge

line. All support documentation can be found on Micrel’s

Precision Edge

®

Features

• Selects between two sources, and provides a glitch-free,

stable LVPECL output

• Guaranteed AC performance over temperature and supply

voltage:

– Wide operating frequency: 1kHz to >1.5GHz

• Unique patent-pending input isolation design minimizes

crosstalk

• Fail-Safe Input prevents oscillations

• Ultra-low jitter design:

• Unique patent-pending input termination and VT pin

accepts DC- and AC-coupled inputs (CML, PECL, LVDS)

• 800mV LVPECL output swing

• 2.5V ±5% or 3.3V ±10% supply voltage

• –40°C to +85°C industrial temperature range

• Available in 24-pin (4mm x 4mm) MLF

Applications

• Redundant clock switchover

• Failsafe clock protection

Markets

• LAN/WAN

• Enterprise servers

• ATE

• Test and measurement