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SY88422L
4.25Gbps Laser Driver with Integrated Bias
General Description
The SY88422L is a single 3.3V supply, small form factor laser driver for telecom/datacom applications up to 4.25Gbps. The driver can deliver modulation current up to 90mA and a bias current up to 100mA. Datasheets and support documentation can be found on Micrel's web site at: www.micrel.com.
Features
* * * * * 35mA power supply current typical Operation up to 4.25Gbps Modulation current up to 90mA Bias current up to 100mA Available in 16-pin small form factor (3mm x 3mm) (R) MLF package
Applications
* Multi-rate LAN, MAN applications up to 4.25Gbps: FC, GbE, SONET/SDH * SFF, SFP, LX-4 Modules ___________________________________________________________________________________________________________
Typical Application
Micrel Inc. * 2180 Fortune Drive * San Jose, CA 95131 * USA * tel +1 (408) 944-0800 * fax + 1 (408) 474-1000 * http://www.micrel.com
November 2007
M9999-112607-A hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SY88422L
Ordering Information(1)
Part Number SY88422LMG SY88422LMGTR
Notes: 1. Contact factory for die availability. Dice are guaranteed at TA = +25C, DC Electricals only. 2. Tape and Reel.
(2)
Package Type MLF-16 MLF-16
Operating Range Industrial Industrial
Package Marking 422L with Pb-Free bar-line indicator 422L with Pb-Free bar-line indicator
Lead Finish NiPdAu Pb-Free NiPdAu Pb-Free
Pin Configuration
16-Pin MLF (MLF-16)
(R)
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SY88422L
Pin Description
Pin Name 1, 4, 9, 12 7, 8, 14 2 3 5 6 10 11 13 15 16 Pin Number VCC GND DIN+ DIN- MODSET /EN MOD- MOD+ BIAS BIASMON BIASSET Pin Function Supply Voltage. Bypass with a 0.1F//0.01F low ESR capacitor as close to VCC pin as possible. Ground. Ground and exposed pad must be connected to the plane of the most negative potential. Non-inverting input data. Internally terminated with 50 to a reference voltage. Inverting input data. Internally terminated with 50 to a reference voltage. Modulation current setting and control. The voltage applied to this pin will set the modulation current. Input impedance 25k. Active Low TTL. The driver is disabled when this pin is unconnected or /EN asserted high. The driver is enabled when /EN is asserted low. Inverted modulation current output. Outputs modulation current when input data is negative. Non-inverted modulation current output. Outputs modulation current when input data is positive. BIAS Current Output Bias monitor. Install an external resistor from this pin to GND to convert the output current to a voltage proportional to the bias current Bias current setting. The voltage applied to this pin will set the bias current. Input impedance 25k.
Truth Table
DIN+ L H X
Notes: 1. IMOD = 0 when MOD+ = H. 2. Assuming that the laser cathode is tied to MOD+.
DINH L X
/EN L L H or NC
MOD+ H L H
(1)
MODL H L
Laser Output L H L
(2)
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Micrel, Inc.
SY88422L
Absolute Maximum Ratings(1)
Supply Voltage (VCC) .......................................-0.5V to +4.0V CML Input Voltage (VIN) ......................VCC-1.2V to VCC+0.5V TTL Control Input Voltage (VI) .................................0V to VCC Lead Temperature (soldering, 20sec.) .......................+260C Storage Temperature (Ts) ........................... -65C to +150C
Operating Ratings(2)
Supply Voltage (VCC) ...................................... +3.0V to +3.6V Ambient Temperature (TA) ............................ -40C to +85C (3) Package Thermal Resistance (R) MLF (JA) Still-air .......................................................... 60C/W (JB) ...................................................................... 33C/W
DC Electrical Characteristics
TA = -40C to +85C and VCC = +3.0V to +3.6V, unless otherwise noted. Typical values are VCC = +3.3V, TA = 25C, IMOD = 30mA, IBIAS = 20mA.
Symbol ICC VMOD_C VBIAS_C RIN(DATA) VDIFF_IN (DIN) VIL (/EN) VIH (/EN) RIN (MODSET) VMODSET RIN (BIASSET) VBIASSET
Notes: 1. Permanent device damage may occur if absolute maximum ratings are exceeded. This is a stress rating only and functional operation is not implied at conditions other than those detailed in the operational sections of this data sheet. Exposure to absolute maximum ratings conditions for extended periods may affect device reliability. 2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings. 3. Package Thermal Resistance assumes exposed pad is soldered (or equivalent) to the devices most negative potential on the PCB. JB uses a 4layer and JA in still air unless otherwise stated. 4. ICC = 56mA for worst-case conditions with IMOD = 90mA and BIAS=100 mA, TA = +85C, VCC = 3.6V.
Parameter Power Supply Current Compliance Voltage Compliance Voltage Input Resistance at DIN+, DIN-, Single Ended Differential Input Voltage Swing Input Low Voltage Input High Voltage MODSET Input Resistance Voltage Range on MODSET Pin BIASSET Input Resistance Voltage Range on BIASSET Pin
Condition Modulation currents excluded
Min VCC-1.5 VCC-2.3 45 100 2
Typ 35
Max 56
(4)
Units mA V V mVpp V V k
VCC VCC 50 55 2400 0.8 25
IMOD range 10mA to 90mA 25 IBIAS range 10mA to 100mA
1.2 1.2
V k V
November 2007
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M9999-112607-A hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SY88422L
AC Electrical Characteristics
TA = -40C to +85C and VCC = +3.0V to +3.6V, unless otherwise noted. Typical values are VCC = +3.3V, TA = 25C, IMOD = 30mA, IBIAS = 20mA.
Symbol Parameter Data Rate IMOD IMOD_OFF tr tf IBIAS IBias_OFF
Notes: 5. Load = 15.
Condition NRZ
(5)
Min 0.1 10
Typ
Max 4.25 90 150
Units Gbps mA A ps ps psPP mA A
Modulation Current
Laser or equivalent load AC-coupled to the driver Current at MOD+ and MOD- when the device is disabled 20% to 80%, 15 load 20% to 80%, 15 load
Modulation OFF Current Output Current Rise Time Output Current Fall Time Total Jitter Bias Current
(5)
50 50 5
70 70 20 100 150
Bias OFF Current
Current at BIAS when the device is disabled
Test Circuit
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Micrel, Inc.
SY88422L
Typical Characteristics
Functional Characteristics
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Micrel, Inc.
SY88422L
Functional Block Diagram
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M9999-112607-A hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SY88422L
Input and Output Stages
Figure 1a. Simplified Input Stage
Figure 1b. Simplified Output Stage
Interfacing the Input to Differential Logic Drivers
Figure 2a. AC-Coupling to LVPECL Driver
Figure 2b. AC-Coupling to CML Driver
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Micrel, Inc.
SY88422L current and zero ohm (0 ) path for the DC current offering headroom for the driver equal to VCC and almost all the modulation current goes into the laser. The inductor alone will cause signal distortion, and, to improve that, a combination of resistor and inductor can be used as shown in Figure 3. In this case, the headroom of the driver is VCC - R1 * Imod, where Imod is the portion of the modulation current that goes through the pull-up network. The coupling capacitor creates a low-frequency cutoff in the circuit, and its value must be chosen to accommodate the lowest and the highest data rates. If the value of the cap is too high, it will degrade the performance at higher data rates, and, if its value is too small, it won't be able to hold a constant charge between the first bit and the last bit of a long string of identical bits in a low data rate application. This leads in both cases to higher pattern-dependant jitter in the transmitter signal. 0.01- t o - 0 . 1 F is found to be good range for all applications from 155Mbps to 4.25Gbps.
Application Hints
The typical applications drawing on the front page shows how to connect the driver to the laser differentially. To drive the laser single ended, just disconnect MOD- from the laser anode and pull it up to VCC with a resistor equal to the equivalent resistor of the load on MOD+, damping resistor plus the laser equivalent resistor. Differential drive improves transition time and laser response. Driving the laser differentially will also minimize the cross talk with the rest of the circuitry on the board especially the receiver. If we refer to Figure 3, the modulation current out of the driver is split between the pull-up network and the laser. If, for example, the total pull-up resistor is twice the sum of the damping resistor and laser equivalent series resistance, only two thirds (2/3) of the modulation current will be used by the laser. To keep most of the modulation current going through the laser, try to keep the total pull-up resistors as high as possible. One solution consists in using an inductor alone as pull-up, presenting a high impedance path for the modulation
Figure 3. AC-Coupling the Laser to the Driver
November 2007
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M9999-112607-A hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SY88422L
Package Information
16-Pin MicroLeadFrame (MLF-16)
(R)
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. (c) 2007 Micrel, Incorporated.
November 2007
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