sy88212l 3.3v, 2.5gbps laser diode driver with integrated bias and apc 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 2008 m9999 -040908 -a hbwhelp@m icrel.com or (408) 955 - 1690 general description the sy88212l is a single supply 3.3v laser driver for datacom and telecom applications with data rates from 155mbps up to 2.5gbps. the driver can deliver mod u lation current up to 85ma, and provides a high compliance voltage that makes it suitable for high - current oper a tion with the laser dc - coupled to it. the drivers have integrated bias and automatic power control (apc) functions. all support documentation can be found on micrel?s web site at: www .micrel.com . features ? 2.4v minimum laser compliance voltage ? operation up to 2.5gbps ? modulation current up to 85ma ? bias current up to 70ma ? power monitoring ? available in 24 - pin (4mm x 4mm) qfn package applications ? multi - rate lan, man applications up to 2. 5gbps: fc, gbe, sonet oc3/12/24 and sdh stm1/4/8 ? sff, sfp modules markets ? telecom, datacom ___________________________________________________________________________________________________________ typical application
micrel, inc. sy88212l april 2008 2 m9999 -040908 -a hbwhelp@micrel.com or (408) 955 - 1690 ordering information (1) part num ber package type operating range package marking lead finish SY88212LMG qfn -24 indu s trial 212l with pb - free bar - line indicator nipdau pb - free sy88212mgtr (2) qfn -24 indu s trial 212l with pb - free bar - line indicator nipdau pb - free notes: 1. contact factory for die availability. dice are guaranteed at t a = +25c, dc electrical only. 2. tape and reel. pin configuration 24- pin qfn
micrel, inc. sy88212l april 2008 3 m9999 -040908 -a hbwhelp@micrel.com or (408) 955 - 1690 pin description pin number pin name pin function 2 din+ non - inverting input data. internally terminated with 50 ? to a reference vol t age. 3 din - inverting input data. internally terminated with 50 ? to a reference vol t age. 5 /txdisable transmitter complementary txdisable. ttl input. the transmitter is enabled when this pin is asserted high and disabled when this pin is asserted low. a 6.3k ? resistor must be installed between pins 6 and gnd if /txdisable is used as ttl input 6 txdisable transmitter disable. ttl input. the transmitter is enabled when this pin is asserted low and disabled when this pin is asserted high or left open. a 6.3k ? resistor must be installed between pin 5 and gnd if txdisable is used as ttl input. 7 /en active low ttl/cmos. internally pulled - up. pull - down with a 22k ? or lower resistance or apply a low level signal (<0.8 v) to enable bias and modu lation. keep floating or apply a high level (>2 v) to disable. 9 osc internal oscillator setting option. install a 0 ? resistor from this pin to vcc or leave it open to set the frequency. refer to the frequency table. 10 txfault transmitter fault indicator. open collector. active high. 12 pwrmon power monitor. provides a c urrent which is proportional to the sum of bias current and half of modulation current. install a resistor between this pin and gnd to convert that current to a voltage. 13 bias - inverting laser bias current output. pull - up to vcc with a resistor. 14 bia s+ non - inverting laser bias current output, sources current when txdisable is inserted low (see pin 6 description) or /txdisable is inserted high (see pin 5 description). connect to the cathode of the laser through a resistor. 16 mod+ non - inverted modula tion current output. provides modulation current when i n put data is positive. 17 mod - inverted modulation current output. provides modulation current when input data is neg a tive. 20 md input from the laser monitoring photodiode. connect to the anode of t he photodiode for apc operation. 22 biasmax install a resistor between this pin and gnd to set the maximum bias current for the closed loop operation. the apc loop controls the bias current up to the level of biasmax. when the bias current reaches the max imum value set through this pin, the driver continues to sink a current equal to this maximum. for open loop operations, this pin sets the bias current. 23 modset modulation current setting and control. the modulation current is set by installing an exte rnal resistor from this pin to ground or using a current source. 24 apcset bias current setting and control. the bias current is set by installing an external resistor from this pin to ground or using a current source. connect a 50k resistor to gnd for op en loop operation. 8, 11,19 gnd ground. ground and exposed pad must be connected to the plane of the most negative potential. 1, 4, 15, 18, 21 vcc supply voltage. bypass with a 0.1f//0.01f low esr capacitor as close to vcc pin as possible. truth tab le din+ din - /en mod+ (1) mod - laser output (2) l h l h l l h l l l h h x x h h l l oscillator frequency osc frequency (mhz) open 25 vcc 50 notes: 1. i mod = 0 when mod+ = h. 2. assuming that the cathode of the laser is tied to mod+.
micrel, inc. sy88212l april 2008 4 m9999 -040908 -a hbwhelp@micrel.com or (408) 955 - 1690 absolute maxi mum 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 +0.3v lead temperature (soldering, 20sec.) ..................... +260c storage temperature (t s ) ......................... ? 65c to +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 ........................................................ 50c/w ( jb ) ................................................................... 30c/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 = 25ma, i bias = 20ma. symbol parameter condition min typ max units i cc power supply current modulation and bias currents excluded 55 95 (4) ma v mod_min minimum voltage required at the driver output, mod+ and mod -, for proper operation 0.6 v v bias_min minimum voltage required at the driver output, bias+ and bias -, fo r proper operation 0.8 v i bias bias - on current voltage at bias pin 0.8v 1 70 ma i bias_off bias - off current current at bias pin when /en is high or txdisable is high 150 a r in input resistance at din+ and din - single ended 42.5 50 57.5 ? v diff - in (din) differential input voltage swing 100 2400 mv pp v ol apcfault output low i ol = 2ma 0.5 v i oh apcfault output leakage v oh = v cc 100 a v ih high voltage /en, txdisable, /txdisable 2 v v il low voltage /en, txdisable, /txdisable 0.8 v v pwrmon maximum voltage at pwrmon pin 1.25 v i md current range at md pin 50 1500 a notes: 1. permanent device damage may occur if absolute maximum ratings are exceeded. this is a stress rating only and functi onal 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 guara nteed 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 4 - layer and ja in still air unless otherwise stated. 4. i cc = 95ma for worst - case conditions with i mod = 85ma, i bias = 70ma, t a = +85c, v cc = 3.6v.
micrel, inc. sy88212l march 2008 5 m9999 - 030708-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 otherwi se noted, typical values are v cc = +3.3v, t a = 25c, i mod = 25ma, i bias = 20ma . symbol parameter condition min typ max units data rate nrz 0.155 2.5 gbps i mod modulation current (5) ac - coupled 10 85 ma dc- coupled, voltage at mod pin 0.6v 10 70 (6) ma i mod_off modulation off current current at mod+ when /en is high or txdisable is low 150 a current at mod - when /en is high or txdisable is high 150 a t r output current rise time 20% to 80%, i mod = 60ma 60 85 ps t f output current fall tim e 20% to 80%, i mod = 60ma 60 85 ps jitter total jitter (7) 155mbps data rate 30 ps pp 622mbps data rate 30 1.25gbps data rate 30 2.5gbps data rate 30 t init apc loop initialization time power up with /en low 12 s /en changes from high to low with power on. 10 s notes: 5. load = 15 ?. 6. assuming v cc = 3.0v, laser bandgap voltage = 1v, laser package inductance = 1nh, laser equivalent series resistor = 5 ?, and damping resist or = 10 ?. 7. total jitter is measured using 2 7 ? 1 prbs patte rn.
micrel, inc. sy88212l march 2008 6 m9999 - 030708-a hbwhelp@micrel.com or (408) 955 - 1690 functional diagram
micrel, inc. sy88212l march 2008 7 m9999 - 030708-a hbwhelp@micrel.com or (408) 955 - 1690 detailed functional description the sy88212l laser driver is comprised from a fast modulator, a fast bias circuit, and a digital apc loop that allows for fast laser turn - on time. the driver features a power monitoring functi on. bias and modulation setting bias and modulation currents are set by installing resistors from apcset (pin 24) to ground and from modset (pin 23) to ground respectively or by applying a negative current at those pins. i md variation versus r apcset resist or, i bias variation versus r biasmax resistor, and i mod variation versus r modset resistor are shown on page 8. biasmax a resistor between biasmax pin and ground sets the maximum bias the driver can sink. at normal operation, the bias current tracks the la ser optical power through the laser monitoring photodiode and the apc loop to compensate for any power deviation from the nominal value set at the start of operation using apcset. if for any failure (laser or photodiode degradation, open feedback circuit e tc?) the apc loop keeps increasing the bias current trying to compensate for the low power indication, the bias current will stop increasing when it reaches biasmax value and continues to operate at that maximum value and txfault asserted high. biasmax als o controls the bias current when the circuit is operating in the open loop mode. apc loop function at start up, with the driver enabled, the laser turns on within a few microseconds and its back facet monitoring photodiode starts to generate a photocurren t proportional to the optical power. the photocurrent is fed back to the md pin on the driver where it?s converted to a voltage. the conversion voltage is compared to apcset on the driver. at equilibrium, the feedback voltage equals the apcset voltage and the laser optical power reaches its nominal value. if the laser power deviates from its nominal value, the apc loop brings it back to its nominal setting. apc loop failure txfault is asserted high if the bias current reaches biasmax or if the apc loop cou nter reaches its minimum or its maximum counts. interfacing the driver with the laser diode as shown in the ?typical application? drawing, mod+ pin is connected to the laser cathode through a 10 ? resistor and mod - pin is connected to v cc with a 15 ? resisto r equivalent to 10 ? (damping resistor) in series with the laser (equivalent resistor of 5 ? ). the laser can be driven differentially by connecting mod - to the anode of the laser through 15 ? (15 ? pull - up removed) and isolating the anode of the laser from vcc with an inductor. for better results at 2.5gbps, the driver can be ac - coupled to the laser as shown in figure 1. figure 1. laser ac - coupled to the driver typical application
micrel, inc. sy88212l march 2008 8 m9999 - 030708-a hbwhelp@micrel.com or (408) 955 - 1690 typical characteristics functional characteristics
micrel, inc. sy88212l march 2008 9 m9999 - 030708-a hbwhelp@micrel.com or (408) 955 - 1690 in put and output stages figure 2a. simplified input stage figure 2b. simplified output stage interfacing din input to different logic drivers figure 3a. driving din with pecl outputs figure 3b. driving din with cml outputs
micrel, inc. sy88212l march 2008 10 m9999 - 030708-a hbwhelp@micrel.com or (408) 955 - 1690 package information 24- pin (3mm x 3mm) 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 responsibil ity 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, devic es 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 a nd purchaser agrees to fully indemni fy micrel for any damages resulting from such use or sale. ? 2008 micrel, incorporated.
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