SY89844U Datasheet, PDF (1/18 Pages) Micrel Semiconductor – Precision LVDS Runt Pulse Eliminator 2:1 MUX with 1:2 Fanout and Internal Termination

SY89844U
Precision LVDS Runt Pulse Eliminator 2:1
MUX with 1:2 Fanout and Internal Termination
General Description
The SY89844U is a low jitter LVDS, 2:1 input
multiplexer (MUX) optimized for redundant source
switchover applications. Unlike standard
multiplexers, the SY89844U 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 outputs are 325mV LVDS with fast
rise/fall times guaranteed to be less than 150ps.
The SY89844U operates from a 2.5V ±5% supply
and is guaranteed over the full industrial
temperature range of –40°C to +85°C. The
SY89844U 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 LVDS output
• Guaranteed AC performance over temperature
and supply voltage:
– wide operating frequency: 1kHz to >1.5GHz
– <870ps In-to-Out t_pd
– <150ps 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)
• 325mV LVDS output swing
• 2.5V +5% power supply
• –40°C to +85°C industrial temperature range
• Available in 24-pin (4mm x 4mm) 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.
MicroLeadFrame and MLF are trademarks of Amkor Technology, Inc.
May 2005
M9999-050305
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