Micrel SY88216L User manual

SY88216L
Optical Evaluation Board
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel [phone] • fax + 1 [phone] • http://www.micrel.com
February 2008
M9999-022108-
A
[email protected] or [phone]
General Description
This evaluation board allows for checking the
performance of the SY88216 burst mode driver while
driving a laser.
Datasheet and support documentation can be found on
Micrel's web site at: www.micrel.com.
Features
•Open loop or close-loop operation
•Manual modulation, biasmax and bias setting
Related Support Documentation
•SY88216L Datasheet
_______________________________________________________________________________________________________
Evaluation Board

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 2 M9999-022108-
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TOSA Installation
Check the pin-out of the laser and install according to
the diagrams shown in Figure 1.
Figure 1. Mounting of the Laser
Evaluation Board Setting and Operation
1. Install a jumper on SW3 to enable the driver.
2. Continuous Mode Operation: Connect BEN-
to GND or connect BEN+ to VCC to operate the
chip in continuous mode first.
3. Adjust potentiometers VR2 (BIASMAX), VR3
(MODSET), and VR4 (BIASSET) completely
counterclockwise to set bias and modulation
currents to zero “0” before powering the board.
4. If the inputs DIN+/DIN- are DC-coupled, set
the output of the pattern generator high level
within the range 0.5V-2V, first. Then connect
the input (DIN+/DIN-) to the output of the
pattern generator.
5. Connect the laser output to the optical module
of the scope with a SMF jumper.
6. Open Loop Operation: Install a jumper on
SW2 (MOD ON) and make sure that there is
no jumper on SW4 (PD-MD).
7. Connect 3.3V to TP9 (red) and GND to TP10
(black) to power the board.
8. Turn VR2 (BIASMAX) clockwise, BIASMAX
sets the bias current in open loop, to increase
the bias current until the laser starts output
some light then turn VR3 clockwise to set
modulation current. Keep adjusting bias (VR2)
and modulation (VR3) until an acceptable eye
diagram is seen on the scope.
9. Bias Current can be deduced from the voltage
across R7 between TP4 and TP6.
IBIAS = (VTP6 – VTP4) / R7
10. The voltage between TP11 (BIASMON) and
GND (across R4) is proportional to (Bias
Current + Half modulation current):
(IBIAS + IMOD / 2) / 50 = VR4 / R4
11. Close-loop operation: Install jumpers on SW1
(BIAS ON) and SW4 (PD-MD) to close the
loop and turn VR4 clockwise to increase the
bias current. Keep adjusting BIASSET (VR4)
and modulation (VR3) until an acceptable eye
diagram is seen on the scope.
Performance
Figure 2. Optical Eye Diagram
1.25Gbps with 2.3G Filter
Laser Response Tuning
Overshoot/Undershoot
The damping resistors R21 and R22 installed in series
with the laser are 10Ω. This value might be changed
to a higher value to minimize or suppress any
overshoot or undershoot on the optical signal out of
the laser, but keep in mind that higher value damping
resistors will lead to higher rise/fall time and lower
maximum modulation current.
The user can adjust the values of (R19, C8) and/or
(R8, C9) to get better performance with his laser.

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 3 M9999-022108-
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Burst Mode Operation
1. Use the setup diagram below to perform burst
mode operation measurements.
2. Disconnect BEN+ from VCC and BEN- from
GND whichever is connected and connect
BEN inputs to the output of the BEN signal
generator.
3. Connect the trigger output of the BEN signal
generator to the trigger input on the scope.
4. Select the frequency of the BEN signal to have
BEN high for at least 100ns per cycle to give
enough time to the optical signal to settle.
Performance

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 4 M9999-022108-
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Evaluation Board Timing Set-Up

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 5 M9999-022108-
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Evaluation Board Schematic

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 6 M9999-022108-
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PCB Layout/Assembly

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 7 M9999-022108-
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Bill of Materials
Item Part Number Manufacturer Description Qty.
C1-5, C10 Vishay(1) 0.1µF, Size 0402, Ceramic Capacitor 6
C6, C7 ECSH0GY106R Panasonic(2) 10µF, Y, Tantalium Solid Electrolytic Capacitor 2
C8 Vishay(1) 5pF, Size 0402, Ceramic Capacitor 1
D1 67-1636-1-ND Digikey(3) Red LED 1
J1, J3-5 142-0701-851 Johnson
Components(4)
SMA End Launch Receptacle Connector 4
J2 Vishay(1) TOSA, Laser Subassembly 1
L1 Vishay(1) 1.2µH Ferrite Bead Inductor, Size 1206 1
L2 Vishay(1) 0ΩResistor 1
L3 Vishay(1) 1.2µH Ferrite Bead Inductor, Size 0805 1
Q3, Q4 MMTB3906WT1 ON Semiconductor(5) N-MOSFET 2
R6, R13,
R14
CRCW04020R00F Vishay(1) 0ΩResistor 3
R3, R7, R9,
R21, R22
CRCW040210R0F Vishay(1) 10ΩResistor 5
R19 CRCW040275R0F Vishay(1) 75ΩResistor 1
R16, R18 CRCW040282R0F Vishay(1) 82ΩResistor 2
R1, R2, R4 CRCW04021000F Vishay(1) 100ΩResistor 3
R15, R17 CRCW04021300F Vishay(1) 130ΩResistor 2
R12 CRCW04022700F Vishay(1) 270ΩResistor 1
R11 CRCW04021002F Vishay(1) 10kΩResistor 1
SW1, SW2,
SW3, SW4
TSW-1-2-07-G-S Samtec(6) Header, 2 positions 4
TP10 5011 Keystone(7) Color Coded PCB test point, Black 1
TP1-TP8,
TP11
5014 Keystone(7) Color Coded PCB test point, Yellow 9
TP9 5010 Keystone(7) Color Coded PCB test point, Red 1
U1 SY88216L Micrel, Inc.(8) 2.5G Burst Mode Laser Driver 1
VR2, VR3,
VR4
3269 W-1-503 GLF Bourns(9) 50K SMD Trimming Potentiometer 3
Notes:
1. Vishay:
www.vishay.com.
2. Panasonic:
www.panasonic.com.
3. Digikey:
www.digikey.com.
4. Johnson components: www.johnsoncomponents.com.
5. ON Semiconductor: www.onsemi.com.
6. Samtec:
www.samtec.com.
7. Keystone:
www.keyelco.com.
8. Micrel, Inc.: www.micrel.com.
9. Bourns:
www.bourns.com.

Micrel, Inc. SY88216L Optical Evaluation Board
February 2008 8 M9999-022108-
A
[email protected] or [phone]
HBW Support
Hotline: [phone]
Email Support: [e-mail]
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL [phone] FAX [phone] 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 fo
r
its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
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p
orated.