2.0GHz, Low Power, 1:6 LVPECL Fanout Buffer with 2:1

2.0GHz, Low Power, 1:6 LVPECL
Fanout Buffer with 2:1 Input MUX
and Internal Termination
SY89856U Evaluation Board
General Description
Features
The SY89856U evaluation board is designed for
convenient setup and quick evaluation of the
SY89856U. The board is optimized to interface directly
to a 50Ω oscilloscope.
For best AC performance, the board is configured in ACcoupled In and AC-coupled Out configuration. For
applications that require a DC-coupled configuration,
step-by-step instructions for modifying the board are
included.
•
Fully assembled and tested SY89856U
•
+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-coupling operation
Related Documentation
•
SY89856U 2.0GHz, Low Power, 1:6 LVPECL
Fanout Buffer with 2:1 Input MUX and Internal
Termination Data Sheet
_______________________________________________________________________________________________________
Evaluation Board
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.
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 2005
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Evaluation Board Description
The default configuration for the SY89856U board is
AC-coupled. The choice between AC-coupled and DCcoupled configurations offers the user flexibility for
specific applications. With the current board layout, Q0
is meant for DC-coupled operation. In default ACcoupled configuration, Q0 is not brought out.
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.
March 2005
SY89856U Evaluation Board
DC-Coupled Evaluation Board
For applications that are not suited to AC-coupling such
as clock applications that can be turned off for extended
periods of time, the board can be user-configured for
DC-coupled operation.
This can be accomplished by modifying the board to use
two power supplies into a “split-supply configuration”.
Since LVPECL is referenced to VCC, and standard PECL
termination is 50Ω to VCC-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
provides the correct terminations for the device by
setting the Ground potential on the board to be exactly 2
volts below the VCC supply. The VEE voltage is then set
to –1.3V for 3.3V devices, or –0.5V for 2.5V devices to
ensure proper VCC to VEE voltage difference.
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.
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SY89856U Evaluation Board
Evaluation Board
AC-Coupled Evaluation Board
I/O
Power Supply
VCC
GND
VEE
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. AC-Coupled Evaluation Board Power Supply Connections
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SY89856U Evaluation Board
Evaluation Board
DC-Coupled Evaluation Board
I/O
Power Supply
VCC
GND
VEE
DC-Coupled Input/DC-Coupled Output
2.5V
+2.0V
0V
-0.5V
DC-Coupled Input/DC-Coupled Output
3.3V
+2.0V
0V
-1.3V
Table 2. DC-Coupled Evaluation Board Power Supply Connections
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SY89856U Evaluation Board
7. Using equal length 50Ω impedance coaxial
cables, connect the signal source to the inputs
on the evaluation board (SMA1 and SMA2 or
SMA3 and SMA4).
AC-Coupled Evaluation Board Setup
Setting up the SY89856U AC-coupled Evaluation
Board
The following steps describe the procedure for setting
up the evaluation board:
1. Set the voltage setting for a DC supply to be
either 2.5V or 3.3V depending upon your
application and turn off the supply.
2. Connect the GND and VEE terminal to the
negative side of a DC power supply. This is the
0V ground potential.
3. Connect the VCC terminal to the positive side of
a DC power supply.
4. Turn on the power supply and verify the power
supply current is <160mA.
5. Turn off the power supply.
6. Using a differential signal source, set the
amplitude of each side of the differential pair to
be 800mV (1600mV measured differentially).
Set the offset to be a positive value, the value of
this offset is not critical, since the AC-coupled
inputs will automatically bias to the correct
offset. Turn off or disable the outputs of the
signal source.
March 2005
8. Using equal length 50Ω impedance coaxial
cables, connect the outputs of the evaluation
board (SMA5 and SMA6 or SMA7 and SMA8 or
SMA9 and SMA10 or SMA11 and SMA12 or
SMA13 and SMA14 or to the oscilloscope or
other measurement device that has an internal
50Ω termination. Any of these 10 outputs that
are not connected to a scope or other
instrument should be terminated with a 50Ω to
ground at the SMA on the board.
9. Turn on the power supply and verify the current
is <200mA.
10. Enable the signal source and monitor the
outputs.
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SY89856U Evaluation Board
5. Turn on the power supply and verify that the
power supply current is <160mA. Using a
voltmeter.
6. Turn off the power supply.
7. Disable the outputs of the differential signal
source and set the VOH = VCC–1.0V and the VOL =
VCC–1.75V) as shown in the following table:
Modifying AC-Coupled Outputs for DCCoupled Operation
When DC-coupling is Necessary
For applications when AC-coupling is not appropriate,
the board can be reconfigured for DC-coupled
operation. An example when DC-coupling is required is
if the input data or clock can be disabled. This would
result in a DC-signal at the inputs and the on-board
biasing resistors (R1 and R2) would apply the same
level to both the true and complement inputs. Since
these inputs are differential, this would result in an
intermediate non-differential state at the inputs and the
outputs would be in an indeterminate condition.
Reconfiguring the board for DC-coupled operation and
using two power supplies can avoid this condition.
Reconfiguring the AC-coupled Board into a DCcoupled Board
The following procedure details the steps for converting
an AC-coupled board to a DC-coupled board:
I/O Voltage Level
+3.3V Supply
+2.5V Supply
VOH = VCC–1.0V
+2.3V
+1.5V
VOL = VCC–1.75V
+1.55V
+0.75V
Table 3. LVPECL I/O Levels
8. Using equal length 50Ω impedance coaxial
cables, connect the outputs of the evaluation
board (SMA5 and SMA6 or SMA7 and SMA8 or
SMA9 and SMA10 or SMA11 and SMA12 or
SMA13 and SMA14 or SMA15 and SMA16) to
the oscilloscope or other measurement device
that has an internal 50Ω termination. Any of
these 12 outputs that are not connected to a
scope or other instrument should be terminated
with a 50Ω termination-to-ground at the SMA on
the board.
9. Turn on the power and verify the current is
<200mA.
10. Enable the signal source and monitor the
outputs.
1. Disconnect VREF-AC0 and VT0
2. Disconnect VREF-AC1 and VT1
3. Remove resistors R2-R11
4. Replace capacitors C1–C4 and C7–C16 with 0Ω
resistors.
Setting up the DC-coupled Evaluation Board
The following steps describe the procedure for setting
up the DC-coupled evaluation board:
1. Set the voltage for DC supply number 1 to be
2.0V and connect it to J1 (VCC).
2. Set the voltage for DC supply number 2 to be –
1.3V (for 3.3V operation) or –0.5V (for 2.5V
operation) and connect it to J3 (VEE).
3. Connect the negative side of power supply 1 to
the positive side of power supply 2. This is the 0V
ground potential for the board.
4. Turn off the power supplies and connect the
GND terminal on the board, J2, to the negative
side of a DC power supply 1 and the positive side
of DC power supply 2
Evaluation Board Layout
PC Board Layout
The evaluation board is constructed with Rogers
4003 material and is coplanar in design, fabricated to
minimize noise, achieve high bandwidth and
minimize crosstalk.
L1
GND and Signal
L2
GND
L3
VCC
L4
GND
Table 4. Layer Stack
March 2005
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SY89856U Evaluation Board
Bill of Materials
Item
Part Number
Manufacturer
(1)
C1-C18
C21, C22
VJ0402Y104KXXAT
Vishay
C19, C20
293D685X0025C2T
Vishay(1)
J1
J2, J3
R1
111-0702-001
111-0703-001
CRCW04023001F
Description
Qty.
0.1µF, 25V, 10% Ceramic Capacitor, Size 0402, X7R
Dielectric
20
6.8µF, 20V, Tantalum Electrolytic Capacitor, Size C
2
Johnson
(2)
Red Banana Jack
1
Johnson
(2)
Black Banana Jack
2
(1)
3kΩ, 10%, 1/16W Resistor SMD, Size 0402
1
(1)
82Ω, 1/10W, 5% Thick-film Resistor, Size 0402
10
Jack Assembly End Launch SMA
16
Vishay
R2-R11
CRCW040282R5F
SMA1SMA16
142-0701-851
Johnson(2)
Vishay
SW1
CT2182LPST-ND
DigiKey(3)
2-Position Dip
1
U1
SY89856U
Micrel(4)
2.0GHz, Low-Power, 1:6 LVPECL Fanout Buffer with 2:1
Input MUX and Internal Termination
1
Additional Components for AC-Coupled Outputs
Item
C1-C4,
C7-C18
Part Number
CRCW0402000F
Manufacturer
(1)
Vishay
Description
Qty.
0Ω, 1/16W, Resistor SMD, Size 0402
16
Notes:
1. Vishay: www.vishay.com.
2. Johnson: www.johnsoncomponents.com.
3. DigiKey: www.digikey.com.
4. Micrel, Inc.: www.micrel.com.
March 2005
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SY89856U Evaluation Board
Micrel Cross Reference
Application Hints and Notes
To find an equivalent Micrel part, go to Micrel’s
website at: http://www.micrel.com and follow the steps
below:
1. Click on Dynamic Cross Reference.
2. Enter competitor’s part number in the Dynamic
Cross Reference field.
3. To download a PDF version of this information,
click on the Cross Reference PDF tab.
For application notes on high speed termination on
PECL and LVPECL products, clock synthesizer
products, SONET jitter measurement, and other High
Bandwidth products go to Micrel’s website at
http://www.micrel.com/. Once in Micrel’s website,
follow the steps below:
1. Click on “Product Info.”
2. In the Applications Information Box, choose
“Application Hints and Application Notes.”
HBW Support
Hotline: 408-955-1690
Email Support: [email protected]
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a
product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for
surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury
to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and
Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Incorporated.
March 2005
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