SY89842U Datasheet, PDF (1/16 Pages) Micrel Semiconductor – Precision CML Runt Pulse Eliminator 2:1 Multiplexer

SY89842U
Precision CML Runt Pulse Eliminator 2:1
Multiplexer
General Description
The SY89842U is a low jitter CML, 2:1 differential
input multiplexer (MUX) optimized for redundant
source switchover applications. Unlike standard
multiplexers, the SY89842U 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) as small as 100mV (200mV_PP) without any
level shifting or termination resistor networks in the
signal path. The output is 400mV CML with fast
rise/fall times guaranteed to be less than 80ps.
The SY89842U 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
SY89842U is part of Micrel’s high-speed, Precision
Edge^® product line. All support documentation can
be found on Micrel’s web site at: www.micrel.com.
Features
Precision Edge^®
• Selects between two sources, and provides a glitch-
free, stable CML output
• Guaranteed AC performance over temperature and
supply voltage:
– Wide operating frequency: 1kHz to >1.5GHz
– < 840ps In-to-Out t_pd
– < 80ps t_r/t_f
• Unique, patent-pending input isolation design
minimizes crosstalk
• Fail-safe input prevents oscillations
• Ultra-low jitter design:
– <1ps_RMS random jitter
– <1ps_RMS cycle-to-cycle jitter
– <10ps_PP total jitter (clock)
– <0.7ps_RMS MUX crosstalk induced jitter
• Unique patent-pending input termination and VT pin
accepts DC- and AC-coupled inputs (CML, PECL,
LVDS)
• 400mV CML output swing
• 2.5V ±5% or 3.3V ±10% supply voltage
• -40°C to +85°C industrial temperature range
• Available in 16-pin (3mm x 3mm) MLF™ package
Applications
• Redundant clock switchover
• Fail-safe clock protection
Markets
• LAN/WAN
• Enterprise servers
• ATE
• Test and measurement
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 [phone] • fax + 1 [phone] • http://www.micrel.com
March 2005
M9999-030805
[e-mail] or [phone]