Microchip SY89846/7U Bedienungsanleitung


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Precision 1:5 LVDS and LVPECL
Fanout Buffer with 2:1 MUX and Fail-
Safe Input with Internal Termination
SY89846/847U 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
March 2007
M9999-030607-A
hbwhelp@micrel.com or (408) 955-1690
General Description
The SY89846U and SY89847U evaluation boards are
designed for convenient setup and quick evaluation
with SMA connectors on each I/O. The board is
optimized to interface directly to a 50Ω oscilloscope.
The board is designed in multiple layers for better
performance and simple signal evaluation. For best
AC performance, the board is 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 datasheets and support documentation can be
found on Micrel’s website at: www.micrel.com.
Features
• SY89846U LVPECL outputs
• SY89847U LVDS outputs
• SMA I/O connectors
• +2.5V or +3.3V power supply
• 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
• SY89846U, Precision 1:5 LVPECL Fanout with 2:1
MUX and Fail-Safe Input with Internal Termination
Datasheet
•
SY89847U, Precision 1:5 LVDS Fanout with 2:1
MUX and Fail-Safe Input with Internal Termination
Datasheet
____________________________________________________________________________________
Evaluation Board
Micrel, Inc.
SY89846/847U Evaluation Board
March 2007
M9999-030607-A
hbwhelp@micrel.com or (408) 955-1690
2
Evaluation Board Description
The SY89846U and SY89847U share a common
evaluation board. The individual evaluation boards
are labeled to identify the specific device on that
board. The SY89847U is an LVDS-output evaluation
board and the SY89846U is an LVPECL-output
evaluation board.
The default configuration for the boards is the AC-
coupled configuration. The choice between two
configurations offers flexibility for different
applications.
AC-Coupled Evaluation Board
The AC-coupled configuration is suited for 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
when interfacing to a variety of signal sources.
The DC-bias levels and AC-coupling capacitors are
supplied on-board for each input. The user only
needs 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
SY89846U
For DC-coupled operation, the boards can be
modified to use two power supplies in a “split-supply
configuration”. The term split-supply simply means
the +3.3V supply is split into a +2V and –1.3V, or for a
+2.5V supply it is split into a +2V and –0.5V power
supply configuration. This effectively offsets the board
by +2V. The +2V offset in this two-power supply
configuration then provides the correct terminations
for the device by setting the ground potential on the
board to be exactly 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 so the device power pins still
see a full 3.3V or 2.5V potential between V
CC
and V
EE
.
Step-by-step instructions for modifying an AC-coupled
evaluation board for DC-coupled operation are
supplied in the sub-section, “Modifying your AC-
Coupled Board for DC-Coupled Operation.”
SY89847U
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 ground level. Therefore, a 2.5V
supply will be split into +1.2V and -1.3V to ensure a
proper V
CC
to V
EE
voltage difference.
Micrel, Inc.
SY89846/847U Evaluation Board
March 2007
M9999-030607-A
hbwhelp@micrel.com or (408) 955-1690
3
Evaluation Board
SY89846U 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
AC-Coupled Input/DC-Coupled Output 2.5V 2.0V 0V -0.5V
AC-Coupled Input/DC-Coupled Output 3.3V 2.0V 0V -1.3V
Table 1. SY89846U AC/DC-Coupled Evaluation Board Power Supply Connections


Produktspezifikationen

Marke: Microchip
Kategorie: Nicht kategorisiert
Modell: SY89846/7U

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