Microchip SY89464U Bedienungsanleitung


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Precision LVPECL/LVDS Runt Pulse
Eliminator 1:10 Fanout Buffer with 2:1
MUX and Internal Termination
SY89464/465U Evaluation Board
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2006
M9999-071106-
C
hbwhelp@micrel.com or (408) 955-1690
General Description
The SY89464/465U evaluation board is designed for
convenient setup and quick evaluation of the
SY89464U, and SY89465U. The boards are optimized
to interface directly to a 50Ω oscilloscope.
For best AC performance, the boards are configured in
AC-coupled In and AC-coupled Out configuration. For
applications that require a DC-coupled configuration,
step-by-step instructions for modifying the board are
included.
All data sheets and support documentation can be found
on Micrel’s web site at: www.micrel.com.
Features
• +2.5V or +3.3V power supply for the SY89464U
• +2.5V power supply for the SY89465U
• AC-coupled configuration for ease-of-use
• I/O interface includes on-board termination
• Fully assembled and tested
• Can be reconfigured for DC-coupled operation
Related Documentation
• SY89464U, Precision LVPECL Runt Pulse Eliminator
1:10 Fanout Buffer with 2:1 MUX and Internal
Termination Data Sheet
• SY89465U, Precision LVDS Runt Pulse Eliminator
1:10 Fanout Buffer with 2:1 MUX and Internal
Termination Data Sheet
_______________________________________________________________________________________________________
Evaluation Board
Micrel, Inc. SY89464/465U Evaluation Board
July 2006
2 M9999-071106-
C
hbwhelp@micrel.com or (408) 955-1690
Evaluation Board Description
The default configurations for the SY89464/5U boards
are AC-coupled. The choice between AC-coupled and
DC-coupled configurations offers the user flexibility for
specific applications.
AC-Coupled Evaluation Board
The AC-coupled configuration is suited to most
customer applications and is preferred by the majority of
users because of its ease-of-use. It requires only a
single power supply and offers the most flexibility in
interfacing to a variety of signal sources.
The DC-bias levels and AC-coupling capacitors are
supplied on-board for each input, making it unnecessary
to vary the offset voltage or change any components on
the board as the power supply voltage varies over the
+2.5V +5% and +3.3V +10% operating range. The user
needs only to supply a minimum input voltage swing and
the bias voltage will automatically adjust the input to the
correct level as the power supply voltage varies.
DC-Coupled Evaluation Board
For applications that are not suited to AC-coupling, such
as clock that can be turned off for extended periods of
time, the board can be user-configured for DC-coupled
operation.
SY89464U
DC-coupled operation can be accomplished by
modifying the board to use two power supplies in a
“split-supply configuration.” Since LVPECL is referenced
to V
CC
, and standard PECL termination is 50Ω to V
CC
-
2V, split-supply is an easy method to interface to a 50Ω
(to ground) scope. Therefore, a 3.3V supply will be split
into +2V and –1.3V, and a 2.5V supply will be split into a
+2V and -0.5V.
The +2V offset in this two-power supply configuration
then provides the correct terminations for the device by
setting the GND potential on the board to 2 volts below
the V
CC
supply. The V
EE
voltage is then set to –1.3V for
3.3V devices, or –0.5V for 2.5V devices to ensure
proper V
CC
to V
EE
voltage difference.
SY89465U
DC-coupled operation can be accomplished by
modifying the board to use two power supplies into a
“split-supply configuration.” In order to correctly interface
LVDS to a 50Ω (to ground) scope, V
CC
must be V
OCM
above the GND level. Therefore, a 2.5V supply will be
split into +1.2V and –1.3V to ensure proper V
CC
to V
EE
voltage difference.
Runt Pulse Eliminator
The SY89464/5U evaluation board allows the user to
test the runt pulse eliminator function. The runt pulse
eliminator function prevents any short cycles or “runt”
pulses during switchover.
To see the effects of the runt pulse eliminator function,
disable it by replacing C18 with a 0Ω resistor. Sweep
the frequency of the function generator to see runt
pulses develop. Enable the runt pulse eliminator
function by restoring C18, and perform the same
frequency sweep.
Any-Input Interface
The unique internal input termination sets the input
common mode voltage. This enables the input to
interface with any differential signal over the supply
voltage without modifying the board.
Micrel, Inc. SY89464/465U Evaluation Board
July 2006
3 M9999-071106-
C
hbwhelp@micrel.com or (408) 955-1690
Evaluation Board
SY89464U AC-Coupled Evaluation Board
I/O Power Supply V
CC
GND V
EE
AC-Coupled Input/AC-Coupled Output 2.5V +2.5V 0V 0V
AC-Coupled Input/AC-Coupled Output 3.3V +3.3V 0V 0V
Table 1. SY89464U AC-Coupled Evaluation Board Power Supply Connections


Produktspezifikationen

Marke: Microchip
Kategorie: Nicht kategorisiert
Modell: SY89464U

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