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general description the MAX3643 burst-mode laser driver provides bias and modulation current drive for pon burst-mode ont appli- cations. it is specifically designed for use with a low-cost external controller for the apc (and if desired, amc) loop. a high-speed differential burst-enable input enables the driver to switch the laser from a dark (output off) condition to full on-condition in less than 2ns. when ben is inac- tive, typical modulation and bias currents are 5? each. laser modulation current can be set from 10ma to 85ma and bias current can be set from 1ma to 70ma using the modset and biasset inputs. a sample-and- hold circuit is provided to capture the monitor diode output during short pon bursts, if needed, and the ben high-speed signal is mirrored on an lvcmos output to be used by the controller operating the apc/amc loop. the MAX3643 burst-mode laser driver is packaged in a 4mm x 4mm, 24-pin thin qfn package. it operates from -40? to +85?. applications a/b/g/xgpon ont modules up to 2.5gbps 1.25gbps ieee epon ont modules features 10ma to 85ma modulation current 1ma to 70ma bias current monitor diode sample and hold 45ps output transition time 2ns turn-on/-off time reference voltage generator lvpecl high-speed inputs (data, burst enable) MAX3643 155mbps to 2.5gbps burst-mode laser driver ________________________________________________________________ maxim integrated products 1 part temp range pin-package MAX3643etg -40c to +85c 24 tqfn-ep* MAX3643etg+ -40c to +85c 24 tqfn-ep* ordering information out- bmd mon1 v cc filter +3.3v 3.3v 10nh 75 ? 1k ? benout biasset modset vbset +3.3v 3.3v vmset 3k ? imax 1k ? bcmon 1k ? in- in+ serial data source en gnd vref ben bias mod 130 ? 130 ? 15 ? 82 ? 82 ? z 0 = 50 ? z 0 = 50 ? 3.3v ben- ben+ burst control 130 ? 130 ? 82 ? 82 ? z 0 = 50 ? z 0 = 50 ? MAX3643 pon triplexer and sfp controller ds1875 15 ? out+ 5.6 ? bias+ 5.6 ? bias- 10 ? mdout mdin 27pf 10pf typical application circuit 19-3848; rev 3; 5/12 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed paddle. pin configuration appears at end of data sheet.
MAX3643 155mbps to 2.5gbps burst-mode laser driver 2 _______________________________________________________________________________________ absolute maximum ratings operating conditions stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. supply voltage v cc ..............................................-0.5v to +4.0v current into bias-, bias+, out-, out+ .......-20ma to +150ma voltage at vmset, vbset, in+, in-, ben+, ben-, en , mdin, mdout, benout, bcmon ...................-0.5v to (v cc + 0.5v) voltage at modset, biasset, vref, imax ........-0.5v to +3.0v voltage at out-, out+, bias-, bias+ .....+0.3v to (v cc + 0.5v) continuous power dissipation (t a = +85?) 24-pin tqfn, multilayer board (derate 27.8mw/? above +85?) ............................1807mw operating temperature range ...........................-40? to +85? storage temperature range ............................-55? to +150? lead temperature (soldering, 10s) .................................+300? soldering temperature (reflow) lead(pb)-free..............................................................+260? containing lead(pb) ....................................................+240? parameter symbol conditions min typ max units supply turn-on time 10% to 90% 0.001 1000 ms ambient temperature -40 +85 c data rate 2500 mbps voltage at vmset, vbset 0 1.4 v voltage at bcmon 0 1.4 v voltage at mdin 0 2.56 v electrical characteristics (v cc = 3.0v to 3.6v, t a = -40? to +85?. typical values are at v cc = 3.3v, t a = +25?, i bias = 20ma, i mod = 30ma, unless other- wise noted.) (note 1) parameter symbol conditions min typ max units supply current i cc excluding laser bias and mode currents, max at i mod = 85ma, i bias = 70ma 32 51 ma i/o specifications lvpecl differential input v in v in = (v in+ ) - (v in- ) 200 1600 mv p-p lvpecl common-mode input voltage v cm v cc - 1.49 v cc - 1.32 v cc - v in / 4 v lvcmos output high voltage i oh = -100a v cc - 0.2 v lvcmos output low voltage i ol = 100a 0.2 v benout propagation dela y t d c l = 20pf, from ben zero crossing to 67% cmos level 30 ns lvcmos input pullup 75 k lvcmos input current v in = 0v or v in = v cc 50 a lvcmos input high voltage 2.0 v cc v lvcmos input low voltage 0.2 0.8 v bias generator specifications bias current range i bias v bias+ , v bias- 0.6v 1 70 ma bias current, burst off i bias, off ben = low or en = high 5 50 a 1ma i bias < 2ma, vbset = vref 88 2ma i bias < 10ma, vbset = vref 70 88 110 biasset current gain g bias 10ma i bias < 70ma, vbset = vref 82.5 88 94.5 ma/ma
MAX3643 155mbps to 2.5gbps burst-mode laser driver _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = 3.0v to 3.6v, t a = -40? to +85?. typical values are at v cc = 3.3v, t a = +25?, i bias = 20ma, i mod = 30ma, unless other- wise noted.) (note 1) parameter symbol conditions min typ max units biasset current gain stability 5ma i bias 70ma (note 13) -4.4 +4.4 % biasset current gain linearity 5ma i bias 70ma (note 14) -3.75 +3.75 % bias current overshoot v cc turn-on/-off < 1s 10 % bias current monitor gain g bsm 2ma i bias 70ma, vbset = vref 11 14 17 ma/a 1ma i bias < 5ma 4 bias current monitor gain stability 5ma i bias 70ma -5 +5 % biasset resistor r bias 40 50 60 modulator specifications modulation current range i mod 10 85 ma modulation current off i mod, off ben = low or en = high or v in = low 5 120 a 10ma i mod < 60ma 0.6 instantaneous voltage at out+ 60ma i mod 85ma 0.75 v modset current gain g mod 10ma < i mod < 85ma, vmset = vref 82.5 88 94.5 ma/ma modset current gain stability (note 13) -4.4 +4.4 % modset current gain linearity (note 14) -2.2 +2.2 % i biasset = 0.15ma, i modset = 0.7ma 0.5 i modset = i biasset = 0.15ma 1.7 i modset = i biasset = 0.4ma 1 modset, biasset gain matching (note 15) i modset = i biasset = 0.55ma 1 % modulation current rise time t r 20% to 80% 45 85 ps modulation current fall time t f 20% to 80% 45 85 ps deterministic jitter (note 3) 17 45 ps p-p random jitter (note 4) 0.8 1.4 ps rms modset resistor r mod 40 50 60 modset, biasset operational amplifier specifications modset, biasset voltage range 0.005 1.4 v voltage error (note 5) 5 mv input leakage vmset and vbset pins 0.1 1.5 a turn-off/-on specifications burst-enable time (notes 2, 6, 7) 2.3 ns burst-disable time (notes 2, 6, 8) 2.0 ns sample/hold specifications mdin voltage range 0.05 2.56 v mdout settling relative to final value at 3s, c l < 20pf 1 mv sample/hold droop after 100s (note 9) 2.56 mv v cc turn-on/-off < 1s, i bias 20ma 10 % bias current overshoot i bias <20ma 2 ma
MAX3643 155mbps to 2.5gbps burst-mode laser driver 4 _______________________________________________________________________________________ note 1: dc parameters are production tested at t a = +25?, guaranteed by design and characterization at t a = -40?. ac parameters are guaranteed by design and characterization. note 2: for 10ma i mod 85ma and 4ma i bias 70ma. note 3: deterministic jitter measured with a continuous pattern of 2 7 -1 prbs, 80 ones, 2 7 -1 prbs, 80 zeros at 1.25gbps, and both lvpecl inputs terminated by the network shown in figure 3. note 4: random jitter, rise time, fall time measured with 0000011111 pattern at 1.25gbps. note 5: voltage difference between vmset and modset or vbset and biasset excluding ir drops. the maximum operating voltage at vmset or vbset must be less than 1.4v for proper operation. note 6: turn-on/-off time is when the ben+/ben- lvpecl inputs are used to control modulation and bias currents. note 7: burst-enable delay is measured between the time at which the rising edge of the differential burst-enable input reaches the midpoint, and the time at which the combined output currents (bias plus modulation) reach 90% of their final level. note 8: burst-disable delay is measured between the time at which the falling edge of the differential burst-enable input reaches the midpoint, and the time at which the combined output currents (bias plus modulation) fall below 10% of the bias-on current. note 9: droop measured with sample/hold output load of 10m ? . note 10: enable delay is measured between the time at which the falling edge of the en input reaches 0.8v, and the time at which the combined output currents (bias plus modulation) reach 90% of their final level. note 11: disable delay is measured between the time at which the rising edge of the en input reaches 2v, and the time at which the combined output currents (bias plus modulation) fall below 10% of the bias-on current. note 12: excelight slt2886-lr laser. note 13: current gain stability = [(gain ?nominal gain) / nominal gain], nominal gain at v cc = 3.3v, t a = +25?. note 14: gain linearity = (gainmax ?gainmin), gainavg = gainmax + gainmin gainavg 2 note 15: gain matching = , nominal at v cc = 3.3v, t a = +25?. mod / mod / mod / gain gainbias gain nom gainbiasnom gain nom gainbiasnom ? electrical characteristics (continued) (v cc = 3.0v to 3.6v, t a = -40? to +85?. typical values are at v cc = 3.3v, t a = +25?, i bias = 20ma, i mod = 30ma, unless other- wise noted.) (note 1) parameter symbol conditions min typ max units sampling error final value measured after 10s (mdout - mdin), burst width > 576ns 3 14 mv bandgap voltage reference specifications vref output r l > 10k , c l < 50pf 1.175 1.235 1.295 v modulation/bias current disable enable time 5ma < i bias , 10ma < i mod (note 10) 5.5 s disable time (notes 2, 11) 375 ns r imax range 3 15 k r imax = 3k 155 r imax = 5k 100 150 current limit (tested with i bias = i mod ) i bias +i mod r imax = 10k 50 75 ma optical evaluation 155.52mbps 49 622.08mbps 45 1.24416gbps 38 eye margin (note 12) 2.48832gbps 18 %
MAX3643 155mbps to 2.5gbps burst-mode laser driver _______________________________________________________________________________________ 5 optical eye diagram (155.52mbps, 117mhz filter, pattern = 2 23 - 1 prbs) MAX3643 toc01 excelight slt2886-lr laser average optical power = -6dbm extinction ratio = 15db mask margin = 49% optical eye diagram (622.08mbps, 467mhz filter, pattern = 2 23 - 1 prbs) MAX3643 toc02 excelight slt2886-lr laser average optical power = -6dbm extinction ratio = 15db mask margin = 45% optical eye diagram (1.24416gbps, 933mhz filter, pattern = 2 23 - 1 prbs) MAX3643 toc03 excelight slt2886-lr laser average optical power = -6dbm extinction ratio = 14db mask margin = 38% optical eye diagram (2.48832gbps, 2.3ghz filter, pattern = 2 23 - 1 prbs) MAX3643 toc04 excelight slt2886-lr laser average optical power = -6dbm extinction ratio = 10db mask margin = 18% electrical eye diagram (2.5gbps, i mod = 30ma, pattern = prbs 2 7 - 1 + 8 0 cid) MAX3643 toc05 100ps/div typical operating characteristics (typical values are at v cc = 3.3v, t a = +25?, data pattern = 2 7 -1 prbs + 80 ones + 2 7 -1 prbs + 80 zeros, unless otherwise noted.) supply current vs. temperature (i bias = 20ma, i mod = 30ma) MAX3643 toc06 temperature ( c) i cc (ma) 80 60 20 40 0 -20 15 20 25 30 35 40 45 50 55 60 10 -40 excludes bias and modulation current
MAX3643 155mbps to 2.5gbps burst-mode laser driver 6 _______________________________________________________________________________________ deterministic jitter vs. modulation amplitude MAX3643 toc07 i mod (ma) dj (ps p-p ) 80 70 50 60 30 40 20 3 6 9 12 15 18 21 24 27 30 0 10 random jitter vs. modulation amplitude MAX3643 toc08 i mod (ma) random jitter (ps rms ) 80 70 50 60 30 40 20 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0.2 10 i mod vs. i modset MAX3643 toc09 i modset ( a) i mod (ma) 800 600 400 200 10 20 30 40 50 60 70 80 90 0 0 1000 i bias vs. i biasset MAX3643 toc10 i biasset ( a) i bias (ma) 800 600 400 200 10 20 30 40 50 60 70 80 90 0 0 1000 bias current monitor gain (i bcmon /i bias ) vs. temperature MAX3643 toc11 temperature ( c) gain (ma/a) 80 60 40 20 0 -20 13 14 15 16 17 12 -40 i mod vs. vmset (r modset = 1k ? ) MAX3643 toc12 vmset (v) i mod (ma p-p ) 0.8 0.4 0.2 0.6 1.0 10 20 30 40 50 60 70 80 90 0 01.2 typical operating characteristics (continued) (typical values are at v cc = 3.3v, t a = +25?, data pattern = 2 7 -1 prbs + 80 ones + 2 7 -1 prbs + 80 zeros, unless otherwise noted.)
MAX3643 155mbps to 2.5gbps burst-mode laser driver _______________________________________________________________________________________ 7 typical operating characteristics (continued) (typical values are at v cc = 3.3v, t a = +25?, data pattern = 2 7 -1 prbs + 80 ones + 2 7 -1 prbs + 80 zeros, unless otherwise noted.) i bias vs. vbset (r biasset = 1k ? ) MAX3643 toc13 vbset (v) i bias (ma) 0.6 0.8 0.2 0.4 10 20 30 40 50 60 70 80 90 0 01.0 timing diagram, burst-on (933mhz filter on out+) MAX3643 toc15 500ps/div v out+ v bias+ v ben+ i bias + i mod current threshold vs. r imax MAX3643 toc14 r imax (k ? ) current threshold (ma) 25 20 5 10 15 20 40 60 80 100 120 140 160 0 030 timing diagram, burst-off (933mhz filter on out+) MAX3643 toc16 500ps/div v out+ v bias+ v ben+ sample/hold (10m ? load, 2. 8 s sample and 100 s hold, mdin = 1.56v) MAX3643 toc17 20 s/div mdout 1.56v 1.22v ben+
MAX3643 155mbps to 2.5gbps burst-mode laser driver 8 _______________________________________________________________________________________ pin description pin name function 1 v cca analog supply voltage 2 in+ noninverted data input, lvpecl compatible 3 in- inverted data input, lvpecl compatible 4 v ccs signal supply voltage 5 ben+ noninverted burst-enable input, lvpecl compatible 6 ben- inverted burst-enable input, lvpecl compatible 7 benout burst-enable output, lvcmos. signal replicates ben input. 8 en enable input lvcmos. active low enables bias and out outputs. 9 bcmon bias current monitor. current out of this pin develops a ground-referenced voltage across an external resistor proportional to the bias current. 10 imax current-limit reference. connect a resistor from imax to gnd to set maximum i bias plus i mod . 11 mdout monitor diode out. analog output for sample/hold. 12 mdin monitor diode in. analog input for sample/hold. 13 bias- connect bias- to v cc through a 10 resistor and switching diode 14 bias+ laser bias current output. modulation current flows into this pin when ben input is high. 15, 18 v cco output supply voltage 16 out+ laser modulation current output. modulation current flows into this pin when both ben and in inputs are high. 17 out- connect out- to laser diode anode through a 15 resistor and switching diode 19 gnd supply ground. this pin must be connected to ground. 20 modset modulation current set. current from this pin to ground sets the laser modulation current. 21 vmset modset reference. a ground-referenced voltage at this point establishes the modset reference. 22 vref reference voltage output. may be used for vmset, vbset. 23 vbset biasset reference. a ground-referenced voltage at this point establishes the biasset reference. 24 biasset bias current set. current from this pin to ground sets the laser bias current. ep exposed paddle (ground). the exposed pad must be soldered to the circuit board ground for proper thermal and electrical operation.
MAX3643 155mbps to 2.5gbps burst-mode laser driver _______________________________________________________________________________________ 9 out+ out- r d 10 ? 15 ? v cc r p l p bias+ r comp c comp bias- benout cmos cmos limit mdin biasset modset vbset v cc v cc v cc i m = 88 x i 1 i 1 v cc vmset bcmon vref r d lvpecl lvpecl limit en imax ben- in- ben+ in+ i b = 88 x i 2 i 2 i bcmon = i b x 0.014 mdout MAX3643 r mod r bias 1.2v figure 1. functional diagram
MAX3643 155mbps to 2.5gbps burst-mode laser driver 10 ______________________________________________________________________________________ detailed description the MAX3643 laser driver includes a bias current gen- erator, bias current monitor, modulation current genera- tor, laser drive outputs, and monitor diode sample and hold. lvpecl-compatible inputs are provided for both high-speed data and burst enable. the high-speed burst-enable input signal is replicated on an lvcmos output for use by the controller. laser diode modulation and bias current generators laser diode modulation current amplitude is controlled by the current out of the modset pin, and bias current by the current out of the biasset pin, according to: i mod = i modset x 88 i bias = i biasset x 88 a voltage source and two op amps are provided to enable i modset and i biasset to be set using either a resistor to ground or a current digital-to-analog convert- er (dac). the high-impedance op amp reference input can be externally controlled, so that the modulation and bias currents can also be set using voltage dacs. laser diode modulation and bias current limiter typical laser diodes have an absolute maximum rating of 150ma. to reduce the possibility of laser damage, the modulation current and bias current are shut off if the sum i mod + i bias attempts to exceed the limit set by r imax ; see the typical operating characteristics . bias current monitor the laser diode bias current can be monitored by measur- ing the voltage across an external load resistor connected from bcmon to ground. for example, a 1k ? resistor from bcmon to ground gives the following relationship: the voltage at bcmon must be below 1.4v for proper operation. output drivers the modulation current ranges from 10ma to 85ma, as set by the current through modset. the laser modula- tion current output out+ is optimized to drive a 15 ? load, and must be dc-coupled. a series damping resis- tor, r d , provides impedance matching to the laser diode. the combined value of the series damping resis- tor and the laser diode equivalent series resistance should be close to 15 ? . an rc shunt compensation network, r comp /c comp , connected between the laser diode cathode and ground should also be provided to reduce optical output aberrations and duty-cycle dis- tortion caused by laser diode parasitic inductance. the values of r comp and c comp can be adjusted to match the laser diode and pcb layout characteristics for opti- mal optical eye performance (refer to application note 274: hfan-02.0: interfacing maxim laser drivers with laser diodes ). the out- pin is connected through a 15 ? resistor and switching diode to the laser diode anode. the switching diode at out- improves the opti- cal output eye and burst-enable delay by better match- ing the laser diode characteristics. for data rates greater than 1gbps, a parallel rl peak- ing network, r p /l p , connected between the laser diode anode and v cc is recommended. this network creates a differential drive for the laser diode to improve rise/fall times and reduce jitter. the values of r p and l p are also adjusted to match the laser diode and pcb layout characteristics for optimal optical eye performance. the bias current ranges from 1ma to 70ma, as set by the current through biasset. current in the bias out- put switches at high speed when bursting; therefore, the bias+ pin should be connected directly through a resistor, equal to r d as determined above, to the laser cathode. the bias- pin is connected through a 10 ? resistor and switching diode to v cc . when the ben input is high, the laser driver sinks bias and modulation current according to the settings at modset and biasset. when the ben input is low, the bias+ and out+ currents both shut off within 2ns. note that when ben is low, the bias current is shunted through the bias- output and the modulation current through the out- output. monitor diode sample and hold laser monitor diode current is only generated when there is an optical output (ben is active). when ben is inactive, the monitor current is zero, reflecting the fact that the laser is off. a sample-and-hold circuit, trig- gered by the state of the ben input, is provided in the MAX3643. during the burst-enable active period, the voltage present at mdin is stored on an internal sam- ple-and-hold capacitor; and during the burst-enable inactive period, that voltage is output on mdout; see the timing diagram in figure 2. while the internal sample-and-hold is sampling (ben active), mdout voltage takes a 1.2v reference level. vigk bcmon bias bsm = 1 ?
MAX3643 155mbps to 2.5gbps burst-mode laser driver ______________________________________________________________________________________ 11 < 2.56mv burst-enable (ben ) in 125 s for bpon/gpon internal mdin voltage sampler benout output 100 s 3 s 1.2v mdout figure 2. sample-and-hold timing diagram enable input an lvcmos input, en , is provided to disable both bias and modulation currents under external control. the maximum time to disable laser current with the en con- trol is 375ns. setting the current limit a current limiter is provided to protect the laser diode by shutting down both bias and modulation currents when total current exceeds a value set by the resistor connected from imax to ground. do not use less than 3k ? r i max . see the i bias + i mod current threshold vs. r imax graph in the typical operating characteristics. programming the modset and biasset inputs to program the laser modulation current using a cur- rent dac, connect vmset to vref, attach the dac to the modset pin and set the current according to: i mod = i modset x 88 to program the laser modulation current using a resis- tor or digital potentiometer, connect vmset to vref, attach a resistor from the modset pin to ground, and set the current according to: to program the laser modulation current using a pwm voltage dac (requiring a high-impedance load), attach a dac output to the vmset pin, connect a resistor from the modset pin to ground as shown in the typical applications circuit , and set the current according to: i v rr mod dac modset mod = + 88 i v rr mod modset mod = + 12 88 .
MAX3643 155mbps to 2.5gbps burst-mode laser driver 12 ______________________________________________________________________________________ this approach can also be used for a conventional volt- age dac output, if desired. in all cases, the voltage at modset must be kept 1.4v, which limits the range of acceptable values for r modset depending on the maxi- mum modulation current. laser diode bias current is set in the same manner as modulation current. lvpecl data/burst-enable inputs the MAX3643 data and ben inputs are biased with an on-chip, high-impedance network. when dc-coupled, the MAX3643 operates properly with signals that meet the ec table input-swing and common-mode require- ments, including lvpecl and most cml. see figure 3 for a termination network that can be used to connect the data and ben inputs to lvpecl data out- puts. other termination networks may also be used, as long as both the input swing and common limits are met. sample-and-hold operation when the MAX3643 internal sample-and-hold is not required, the mdin pin should be connected to ground and the mdout pin unconnected. if the internal sample- and-hold is required, then it is necessary to ensure that the time constant resulting from the monitor diode load resistance and the total load capacitance is compatible with the desired minimum burst interval. it is also neces- sary to make certain that the load at mdout does not exceed the capability of the mdout pin. because the voltage at mdin is not reflected to mdout until after the end of the laser burst, systems using the internal sample-and-hold alone cannot support continu- ous mode operation, often a required feature for module calibration. in this case, the voltage at mdin can also be connected directly to a controller mux input. as long as the total capacitance (including monitor diode intrin- sic capacitance, mdin capacitance, mux off-capaci- tance, and wiring parasitics) is less than 50pf, and the monitor diode load resistor is less than 2k ? , then the sample-and-hold captures a 576ns minimum burst. the MAX3643 typical mdin capacitance is 5pf, typical monitor diode maximum capacitance is 25pf, and the typical capacitance of a mux input in the off-state is 3pf to 5pf. when the mux is in the on-state, the capac- itance at the input is typically 10pf to 20pf. if the minimum burst duration is longer than 576ns, it may be useful to connect an external capacitor in par- allel with the monitor diode load to limit the effects of the data pattern on the monitor diode output. MAX3643 130 ? v cc lvpecl z o = 50 ? z o = 50 ? 130 ? in+/ben+ in-/ben- 82 ? 82 ? figure 3. lvpecl high-speed inputs figure 4. single-ended biasing for burst enable in+ in- ben+ ben- v cmben + (100mv to 800mv) v cmben - (100mv to 800mv) v cmben v cmben = +2.0v 3.3v r 1 = 1.65k ? r 2 = 2.54k ? MAX3643
MAX3643 155mbps to 2.5gbps burst-mode laser driver ______________________________________________________________________________________ 13 applications information running burst-enable single-ended see figure 5 for setting up the single-ended lvttl or lvcmos biasing for burst enable. layout considerations to minimize inductance, keep the connections between the MAX3643 output pins and laser diode as close as possible. place a bypass capacitor as close as possible to each v cc connection. take extra care to minimize stray parasitic capacitance on the bias and mdin pins. use good high-frequency layout tech- niques and multilayer boards with uninterrupted ground planes to minimize emi and crosstalk. laser safety and iec 825 using the MAX3643 laser driver alone does not ensure that a transmitter design is compliant with iec 825. the entire transmitter circuit and component selections must be considered. each user must determine the level of fault tolerance required by the application, recognizing that maxim products are neither designed nor authorized for use as components in systems intended for surgical implant into the body, for applications intended to sup- port or sustain life, or for any other application in which the failure of a maxim product could create a situation where personal injury or death can occur. exposed-paddle package the exposed paddle on the 24-pin tqfn provides a very low thermal resistance path for heat removal from the ic. the pad is also electrical ground on the MAX3643 and must be soldered to the circuit board ground for proper thermal and electrical performance. refer to maxim application note 862: hfan-08.1: thermal considerations of qfn and other exposed- paddle packages for additional information. figure 5. single-ended lvcmos or lvttl biasing for burst enable in+ in- ben+ ben- lvttl or lvcmos high lvttl or lvcmos low v cc r 5 = 5k ? r 4 = 3k ? r 6 = 9k ? v cc r 3 = 5k ? MAX3643 figure 6. simplified input circuit schematic MAX3643 v cc v cc v cc 16k ? 5k ? 5k ? in+/ben+ in-/ben- 24k ? v cc interface model
MAX3643 155mbps to 2.5gbps burst-mode laser driver 14 ______________________________________________________________________________________ chip information transistor count: 2771 process: sige bipolar package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. thin qfn (4mm x 4mm) MAX3643 19 20 21 22 12 3456 *ep 18 17 16 15 14 13 23 24 12 11 10 9 8 7 gnd vmset modset vref biasset *the exposed pad must be connected to ground for proper thermal and electrical performance. v cca in+ in- v ccs ben+ ben- v cco out- v cco bias+ bias- vbset mdin imax mdout bcmon benout en out+ top view + pin configuration package type package code outline no. land pattern no. 24 tqfn-ep t2444-3 21-0139 90-0021
MAX3643 155mbps to 2.5gbps burst-mode laser driver maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidanc e. 15 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2012 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 11/05 initial release. added 155mbps to 2.5gbps to the data sheet/part title. all updated the applications section. 1 in the operating conditions table, changed the data rate from 1250mbps to 2500mbps. 2 1 10/08 in the typical operating characteristics , added the electrical eye diagram graph. 6 2 7/10 replaced the typical application circuit ; added the soldering temperature to the absolute maximum ratings section; updated the optical eye mask margins in the electrical characteristics table; corrected equation in note 14; added the optical eye diagrams to the typical operating characteristics section; updated the pin descriptions for the pins with diodes (13, 17) in the pin description table; updated figure 1; updated the output drivers section; updated the layout considerations section; added the land pattern number to the package information table. 1, 2, 4C10, 12, 13, 14 3 5/12 updated typical application circuit , electrical characteristics table, and typical operating characteristics global conditions, and added bias current overshoot parameter 1C7

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