SY88422L 4.25Gbps Laser Driver with Integrated Bias General Description Features 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. • • • • • 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) QFN 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 [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Ordering Information(1) Part Number SY88422LMG (2) SY88422LMGTR Package Type Operating Range Package Marking Lead Finish QFN-16 Industrial 422L with Pb-Free bar-line indicator NiPdAu Pb-Free QFN-16 Industrial 422L with Pb-Free bar-line indicator NiPdAu Pb-Free Notes: 1. Contact factory for die availability. Dice are guaranteed at TA = +25°C, DC Electricals only. 2. Tape and Reel. Pin Configuration 16-Pin QFN November 2007 2 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Pin Description Pin Name Pin Number Pin Function 1, 4, 9, 12 VCC Supply Voltage. Bypass with a 0.1µF//0.01µF low ESR capacitor as close to VCC pin as possible. 7, 8, 14 GND Ground. Ground and exposed pad must be connected to the plane of the most negative potential. 2 DIN+ Non-inverting input data. Internally terminated with 50Ω to a reference voltage. 3 DIN– Inverting input data. Internally terminated with 50Ω to a reference voltage. 5 MODSET 6 /EN 10 MOD– Inverted modulation current output. Outputs modulation current when input data is negative. 11 MOD+ Non-inverted modulation current output. Outputs modulation current when input data is positive. 13 BIAS 15 BIASMON Bias monitor. Install an external resistor from this pin to GND to convert the output current to a voltage proportional to the bias current 16 BIASSET Bias current setting. The voltage applied to this pin will set the bias current. Input impedance 25kΩ. Modulation current setting and control. The voltage applied to this pin will set the modulation current. Input impedance 25kΩ. 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. BIAS Current Output Truth Table MOD+ (1) MOD- (2) DIN+ DIN- /EN Laser Output L H L H L L H L L L H H X X H or NC H L L Notes: 1. IMOD = 0 when MOD+ = H. 2. Assuming that the laser cathode is tied to MOD+. November 2007 3 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Absolute Maximum Ratings(1) Operating Ratings(2) 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.) ..................... +260°C Storage Temperature (Ts) ......................... –65°C to +150°C Supply Voltage (VCC) .................................... +3.0V to +3.6V Ambient Temperature (TA) .......................... –40°C to +85°C (3) Package Thermal Resistance QFN (θJA) Still-air ........................................................ 60°C/W (ψJB) ................................................................... 33°C/W DC Electrical Characteristics TA = –40°C to +85°C and VCC = +3.0V to +3.6V, unless otherwise noted. Typical values are VCC = +3.3V, TA = 25°C, IMOD = 30mA, IBIAS = 20mA. Symbol Parameter Condition ICC Power Supply Current Modulation currents excluded Min VMOD_C Compliance Voltage VCC-1.5 VBIAS_C Compliance Voltage VCC-2.3 RIN(DATA) Input Resistance at DIN+, DIN-, Single Ended 45 VDIFF_IN (DIN) Differential Input Voltage Swing 100 VIL (/EN) Input Low Voltage VIH (/EN) Input High Voltage RIN (MODSET) MODSET Input Resistance VMODSET Voltage Range on MODSET Pin RIN (BIASSET) BIASSET Input Resistance VBIASSET Voltage Range on BIASSET Pin Typ 35 Max 56 (4) VCC 50 mA V VCC V 55 Ω 2400 mVpp 0.8 V 2 V 25 IMOD range 10mA to 90mA kΩ 1.2 25 IBIAS range 10mA to 100mA Units V kΩ 1.2 V 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. ψJB uses a 4layer and θJA in still air unless otherwise stated. 4. ICC = 56mA for worst-case conditions with IMOD = 90mA and BIAS=100 mA, TA = +85°C, VCC = 3.6V. November 2007 4 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L AC Electrical Characteristics TA = –40°C to +85°C and VCC = +3.0V to +3.6V, unless otherwise noted. Typical values are VCC = +3.3V, TA = 25°C, IMOD = 30mA, IBIAS = 20mA. Symbol Parameter Condition Min Max Units Data Rate NRZ 0.1 Typ 4.25 Gbps 10 90 mA 150 µA IMOD Modulation Current Laser or equivalent load AC-coupled to the driver IMOD_OFF Modulation OFF Current Current at MOD+ and MOD- when the device is disabled tr Output Current Rise Time 20% to 80%, 15 Ω load 50 70 ps tf Output Current Fall Time 20% to 80%, 15 Ω load 50 70 ps IBIAS Bias Current IBias_OFF Bias OFF Current (5) Total Jitter (5) 5 Current at BIAS when the device is disabled 20 psPP 100 mA 150 µA Notes: 5. Load = 15Ω. Test Circuit November 2007 5 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Typical Characteristics Functional Characteristics November 2007 6 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Functional Block Diagram November 2007 7 M9999-112607-A [email protected] 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 2b. AC-Coupling to CML Driver Figure 2a. AC-Coupling to LVPECL Driver November 2007 8 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Application Hints current and zero ohm (0Ω) 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 * αImod, where αImod 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. 0.01µ-to-0.1µF is found to be good range for all applications from 155Mbps to 4.25Gbps. 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 9 M9999-112607-A [email protected] or (408) 955-1690 Micrel, Inc. SY88422L Package Information 16-Pin QFN 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. © 2007 Micrel, Incorporated. November 2007 10 M9999-112607-A [email protected] or (408) 955-1690