sy88422l 4.25g bps laser driver with integrated bias 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 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 mod u lation current up to 90ma and a bias current up to 100ma. datasheets and support document ation 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) qfn package applicatio ns ? multi - rate lan, man applications up to 4.25gbps: fc, gbe, sonet/sdh ? sff, sfp, lx - 4 modules ___________________________________________________________________________________________________________ typical application
micrel, inc. sy88422l november 2007 2 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 ordering information (1 ) part number package type operating range package marking lead finish sy88422lmg qfn -16 indu s trial 422l with pb - free bar - line indicator nipdau pb - free sy88422lmgtr (2) qfn -16 indu s trial 422l with pb - free bar - line indicator nipdau pb - free notes: 1. conta ct factory for die availability. dice are guaranteed at t a = +25c, dc electricals only. 2. tape and reel. pin configuration 16- pin qfn
micrel, inc. sy88422l november 2007 3 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 pin description pin name pin number pin function 1, 4, 9, 12 vcc supply voltage. bypass with a 0.1f//0.01f lo w 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 50 ? to a reference vol t age. 3 din ? in verting input data. internally terminated with 50 ? to a reference vol t age. 5 modset modulation current setting and control. the voltage applied to this pin will set the modul a tion current. input impedance 25k ? . 6 /en active low ttl. the driver is disable d when this pin is unconnected or /en asserted high. the driver is enabled when /en is asserted low. 10 mod ? inverted modulation current output. outputs modulation current when input data is neg a tive. 11 mod+ non - inverted modulation current output. outp uts modulation current when i n put data is positive. 13 bias bias current output 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 curren t setting. the voltage applied to this pin will set the bias current. input impedance 25k ? . truth table din+ din - /en mod+ (1) mod - laser output (2) l h l h l l h l l l h h x x h or nc h l l notes: 1. i mod = 0 when mod+ = h. 2. assuming that the la ser cathode is tied to mod+.
micrel, inc. sy88422l november 2007 4 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 absolute maximum ratings (1) supply voltage (v cc ) .................................... ? 0.5v to +4.0v cml input voltage (v in ) .................... v cc ? 1.2v to v cc +0.5v ttl control input voltage (v i ) ............................... 0v to v cc lead temperature (soldering, 20sec.) ..................... +260c storage temperature (t s ) ......................... ? 65c t o +150c operating ratings (2) supply voltage (v cc ) .................................... +3.0v to +3.6v ambient temperature (t a ) .......................... ? 40c to +85c package thermal resistance (3) qfn ( ja ) still - air ........................................................ 60c/w ( jb ) ................................................................... 33c/w dc electrical characteristics t a = ? 40c to +85c and v cc = +3.0v to +3.6v, unless otherwise noted. typical values are v cc = +3.3v, t a = 25c, i mod = 30ma, i bias = 20ma. symbol parameter condition min typ max units i cc power supply current modulation currents excluded 35 56 (4) ma v mod_c compliance voltage v cc - 1.5 v cc v v bias_c compliance voltage v cc - 2.3 v cc v r in(data) input resistance at din+, din -, single ended 45 50 55 ? v diff_in (din) differential input voltage swing 100 2400 mv pp v il (/en) input low voltage 0.8 v v ih (/en) input high voltage 2 v r in (modset) modset input resistance 25 k ? v modset voltage range on modset pin i mod range 10ma to 90ma 1.2 v r in (biasset) biasset input resi stance 25 k ? v biasset voltage range on biasset pin i bias range 10ma to 100ma 1.2 v notes: 1. permanent device damage may occur if absolute maximum ratings are exceeded. this is a stress rating only and functional opera tion is not implied at conditio ns 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 th e 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 4 - layer and ja in still air unless otherwise stated. 4. i cc = 56ma for worst - case conditions with i mod = 90ma and bias=100 ma, t a = +85c, v cc = 3.6v.
micrel, inc. sy88422l november 2007 5 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 ac electrical characteristics t a = ? 40c to +85c and v cc = +3.0v to +3.6v, unless otherwise noted. typical values are v cc = +3.3v, t a = 25c, i mod = 30ma, i bias = 20ma. symbol parameter condition min typ max units data rate nrz 0.1 4.25 gbps i mod modulation current (5) laser or equivalent load ac - coupled to the driver 10 90 ma i mod_off modu lation off current current at mod+ and mod - when the device is disabled 150 a t r output current rise time 20% to 80%, 15 ? load 50 70 ps t f output current fall time 20% to 80%, 15 ? load 50 70 ps total jitter 20 ps pp i bias bias current (5) 5 100 ma i bias_off bias off current current at bias when the device is disabled 150 a notes: 5. load = 15 ?. test circuit
micrel, inc. sy88422l november 2007 6 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 typical characteristics functional characteristics
micrel, inc. sy88422l november 2007 7 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 functional block diagram
micrel, inc. sy88422l november 2007 8 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 input and output stages figure 1a. simplified input stage figure 1b. simplified output stage interf acing the input to differential logic drivers figure 2a. ac - coupling to lvpecl driver figure 2b. ac - coupling to cml driver
micrel, inc. sy88422l november 2007 9 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 application hints the typical applications drawing on the front page shows how to connect the driver to the laser differe ntially. to drive the laser single ended, just disconnect mod - from the laser anode and pull it up to v cc 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 m odulation 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 current and zero ohm (0 ? ) path for the dc current offering headroom for the driver equal to v cc 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 * i mod , where i mod 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 - to - 0.1 f is found to be good range for all applications from 155mbps to 4.25gbps. figure 3. ac - coupling the laser to the driver
micrel, inc. sy88422l november 2007 10 m9999 - 112607-a hbwhelp@micrel.com or (408) 955 - 1690 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 f urnished by micrel in this data sheet is believed to be accurate and reliable. however, no responsibility is assumed by micre l 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 mal function of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or syste ms 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 signific ant 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.
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