SY89838U_10 Datasheet, PDF (1/16 Pages) Micrel Semiconductor – Precision 1:8 LVDS Clock Fanout Buffer

SY89838U
Precision 1:8 LVDS Clock Fanout Buffer
with 2:1 Runt Pulse Eliminator Input MUX
General Description
The SY89838U is a low jitter, low skew, high-speed
1:8 fanout buffer with a unique, 2:1 differential input
multiplexer (MUX) optimized for redundant source
switchover applications. Unlike standard multiplexers,
the SY89838U 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
200mV). The SY89838U distributes clock frequencies
from 1kHz to 1.5GHz, guaranteed, over temperature
and voltage.
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 200mV (400Mv_PP) without any level
shifting or termination resistor networks in the signal
path. The outputs are 350mV compatible LVDS with
fast rise/fall times guaranteed to be less than 150ps.
The SY89838U operates from a 2.5V ±5% supply and
is guaranteed over the full industrial temperature range
of –40°C to +85°C. For applications that require
800mV LVPECL outputs, consider the SY89837U. The
SY89838U 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 clocks, and provides 8
precision, low skew LVDS output copies
• 2:1 MUX input provides a glitch-free, stable LVDS
output
• Guaranteed AC performance over temperature and
supply voltage:
– Wide operating frequency: 1kHz to >1.5GHz
– <150ps t_r/t_f
– <40ps output-to-output skew
• Unique patent-pending input isolation design
minimizes crosstalk
• Fail-safe input prevents oscillation
• 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)
• 350mV LVDS output swing
• Power supply 2.5V +5%
• –40°C to +85°C industrial temperature range
• Available in 32-pin (5mm x 5mm) QFN package
Applications
• Redundant clock switchover
• Failsafe clock protection
Markets
• LAN/WAN
• Enterprise Servers
• ATE
• Test and Measurements
Precision Edge is a registered trademark of Micrel, Inc
May 2008
M9999-051308-D
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