Microchip SY88982L Manual de Usario

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2.5Gbps FP/DFB Laser Drivers
SY88982L 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
April 2005 M9999-04150
5
hbwhelp@micrel.com or (408) 955-169
0
General Description
The SY88982L evaluation board is designed for fast
evaluation of the SY88982L, SY88782L, and SY88932L
laser drivers.
A picture of the board loaded with SY88982L is shown
below.
All data sheets and support documentation can be found
on Micrel’s web site at: www.micrel.com.
Features
Single 3.3V supply voltage
AC-coupled inputs
AC/DC-coupled outputs
Positive ground to allow for DC-coupling outputs to
test equipment.
AC/DC compliance voltage evaluation
Related Documentation
SY88982L, 3.3V, 2.7Gbps High Current Low Power
Laser Driver for FP/DFB Lasers
_______________________________________________________________________________________________________
Evaluation Board
Micrel, Inc. SY88982L Evaluation Board
April 2005 2M9999-04150
5
hbwhelp@micrel.com or (408) 955-169
0
Evaluation Board Description and
Setting
The evaluation board consists of a four-layer FR4
board. The inputs of the driver are AC-coupled and
are accessible through SMA connectors. The board
has a positive ground (VCC is the ground) that will
allow for DC coupling to the scope if needed. There
are two power supply connectors on the board, TP1
for VCC (Ground) and TP5 (VCC2) to be used for AC
compliance voltage measurement only.
Board Setting
Jumper installed on JP1.
R1 = R2 = 50 to make a 25 load when the scope is
connected to J3-4.
Board Operation
Use SMA connectors, J1-J2, to connect a signal to the
drivers inputs. J3-J4 are the drivers outputs, to be
connected to the scope.
Install a jumper on JP1 for normal operation.
Connect the power supply between TP1 (VCC1) and
TP5 (VEE). TP2 (VCC2) is not connected for normal
operation and is reserved for AC-compliance voltage
measurement.
Adjust the modulation current with potentiometer R4.
The modulation current can be measured with one of
the following methods:
1. Measure the output swing on the scope and
divide it by the load (R1 // 50  or R2 // 50 ).
The board comes with a 25 load (50  //
50).
2. Measure the IM_SET voltage at pin 2 (central
pin) of the potentiometer (R4) and use the
modulation gain curve below to deduce IMOD.
Figure 1. Modulation Gain vs. IM_SET
AC Compliance Voltage Measurement
Remove jumper from JP1 and apply a separate 3.3V
variable voltage source (VCC2) on TP5.
Set modulation current to any value between 10mA
and 90mA. For currents more than 70mA, a lower
load, 15 for example (22//scope), must be used to
avoid saturation of the driver’s output.
Apply a valid signal at the input of the driver to get a
clean eye at the output (MOD-), than decrease VCC2
slowly until the eye at MOD- starts to degrade. Record
the value of VCC2 (VCC2_sat) just before the eye
starts to degrade (the driver starts to saturate). The
compliance voltage is the voltage VMOD-_sat at
MOD- given by:
VMOD-_sat = (R1 x VCC + 50 x VCC2_sat)/(R1+50)
IMOD x 50 x R1/(R1+50).
Where 50 is the scope input impedance.
OFF Modulation Current Measurement
Set the board back to normal operation by
disconnecting TP5 and installing a jumper on JP1.
Connect TP4 to VCC to disable the driver.
Measure the modulation current using methods
described above (board operation section).
Figure 2. Example of Eye Diagram
@ 2.5Gbps with 25
load
Micrel, Inc. SY88982L Evaluation Board
April 2005 3M9999-04150
5
hbwhelp@micrel.com or (408) 955-169
0
Evaluation Board Schematic

Especificaciones del producto

Marca: Microchip
Categoría: No categorizado
Modelo: SY88982L

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