SY89840U_10 Datasheet, PDF (1/15 Pages) Micrel Semiconductor – Precision LVPECL Runt Pulse Eliminator 2:1

SY89840U
Precision LVPECL Runt Pulse Eliminator 2:1
Multiplexer
General Description
The SY89840U is a low jitter PECL, 2:1 differential input
multiplexer (MUX) optimized for redundant source
switchover applications. Unlike standard multiplexers,
the SY89840U 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 800mV, 100K compatible LVPECL with fast
rise/fall times guaranteed to be less than 190ps.
The SY89840U 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 SY89840U 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 LVPECL output
• Guaranteed AC performance over temperature and supply
voltage:
– Wide operating frequency: 1kHz to >1.5GHz
– < 880ps In-to-Out t_pd
– < 190ps 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-coupled 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 16-pin (3mm x 3mm) QFN package
Applications
• Redundant clock switchover
• Failsafe clock protection
Markets
• LAN/WAN
• Enterprise servers
• ATE
• Test and measurement
Precision Edge is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
February 2005
M9999-021705
[e-mail] or [phone]