general description the max3864 is a transimpedance preamplifier forapplications in sdh/sonet systems operating up to 2.5gbps. it features 490na (typ) input-referred noise, 2.0ghz bandwidth, and 2ma input overload. the max3864 operates from a single +3.0v to +5.5v supply. it includes an integrated low-frequency com- pensation capacitor, as well as a filter connection that provides positive bias through a 750 resistor to v cc . these features save external components, simplifying design and assembly into a to-46 header with a photo- diode. the max3864 has a typical optical dynamic range of -24dbm to 0dbm using a pin photodetector. applications sdh/sonet transmission systemspin preamplifier receivers apd preamplifier receivers 2.5gbps atm receivers regenerators for sdh/sonet features ? 490na (typ) input-referred noise ? 2000mhz bandwidth ? 2ma input overload ? 100 differential output impedance ? 112mw power dissipation at +3.3v ? integrated filter resistor ? cml outputs ? single +3.0v to +5.5v supply voltage max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier 19-1790; rev 1; 11/05 evaluation kit available out- gnd filter 12 8 7 gnd out+ n.c. in v cc so top view 3 4 6 5 max3864 0.01 f photodiode 750 v cc v cc gnd filter in 0.1 f out+ out- 0.1 f c filter 400pf 100 max3864 limitingamplifier typical application circuit pin configuration ordering information part temp range pin-package max3864esa -40 c to +85 c 8 so max3864e/d -40 c to +85 c dice* * dice are designed to operate with junction temperatures of -40? to +140? but are tested and guaranteed only at t a = +25?. ________________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. note 1: source capacitance represents the total capacitance at the in pin during characterization of noise and bandwidth parame-ters. noise and bandwidth will be affected by the source capacitance. see the typical operating characteristics for more information. note 2: input-referred noise is calculated as (rms output noise) / (gain at f = 10mhz). noise density is (input-referred noise) /(bandwidth) 1/2 . no external filters are used for the noise measurements. note 3: deterministic jitter is defined as the arithmetic sum of pulse-width distortion and pattern dependent jitter measured with a repeating 20-bit pattern of 00111110101100000101 (k28.5). see typical operating characteristics . supply voltage (v cc - gnd) .................................-0.5v to +6.0v in current..............................................................-4ma to +4ma filter current......................................................-8ma to +8ma voltages at out+, out- .................(v cc - 1.5v) to (v cc + 0.5v) continuous power dissipation (t a = +85?) 8-pin so package (derate 6.7mw/? above +85?) ..436mw storage temperature range .............................-55? to +150? operating junction temperature ......................-55? to +150? processing temperature (die) .........................................+400? lead temperature (soldering, 10s) .................................+300? electrical characteristics(v cc = +3.0v to +5.5v, 100 load between out+ and out-, 0.1? coupling capacitors on out+ and out-, t a = -40? to +85?, unless otherwise noted. typical values are at +3.3v, source capacitance = 0.85pf, and t a = +25?.) (note 1) parameter conditions min typ max units input bias voltage 0.66 0.83 0.99 v supply current 34 63 ma transimpedance differential, measured with 40? p-p input 2100 2750 3400 output impedance single ended (per side) 48 50 52 maximum differential output voltage input = 2ma p-p with 100 differential output termination 220 380 575 mv p-p filter resistor 600 750 930 ac input overload 2 ma p-p dc input overload 1m a input-referred rms noise 490 668 na input-referred noise density bandwidth = 2.0ghz (note 2) 11 pa/ hz small-signal bandwidth 1525 2000 mhz low-frequency cutoff -3db, input 20?dc 30 khz transimpedance linear range gain at 40? p-p is within 5% of the small- signal gain 40 ? p-p 3.13v < v cc < 5.5v (note 3) 24 67 deterministic jitter 3.0v v cc 3.13v (note 3) 24 77 ps power-supply rejection ratio (psrr) output referred, f < 2mhz,psrr = -20log( v out / v cc ) 50 db downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier _______________________________________________________________________________________ 3 200 300250 400350 550500 450 600 -40 0 -20 20406080100 input-referred rms noise vs. temperature max3864 toc01 junction temperature ( c) input-referred noise (na rms ) c in = 1.5pf c in = 1.0pf c in = 0.5pf c in is source capacitance presented to die, includes package parasitic, pin diode, and parasitic interconnect capacitance. 50 55 6560 70 75 frequency response max3864 toc02 frequency (mhz) transimpedance (db ) 1 100 10 1k 10k 0 3020 10 40 50 60 70 80 90 100 10 100 1000 10,000 deterministic jitter vs. input amplitude max3864 toc03 input current amplitude ( ap-p) peak-to-peak jitter (ps) 0 300200 100 400 500 600 700 800 900 1000 1 10 100 1000 input-referred rms noise current vs. dc input current max3864 toc04 dc input current ( a) input-referred noise (na rms ) 60 6362 61 6564 6968 67 66 70 -40-200 20406080100 small-signal transimpedance vs. temperature max3864 toc05 ambient temperature ( c) transimpedance db ) 1.4 1.61.5 1.91.8 1.7 2.22.1 2.0 2.3 -40 0 20 -20 406080100 bandwidth vs. temperature max3864 toc06 junction temperature ( c) bandwidth (ghz) c in = 1.5pf c in = 1.0pf c in = 0.5pf c in is source capacitance presented to die, includes package parasitic, pin diode, and parasitic interconnect capacitance. 300 360340 320 400380 480460 440 420 500 -40-200 20406080100 differential output amplitude vs. temperature max3864 toc07 ambient temperature ( c) differential output amplitude (mvp-p) input = 2ma eye diagram (input = 2ma p-p ) max3864 toc11 80ps/div 50mv/div input = 2 13 -1 prbs with 72 cid v cc = 3.0v at t a = -40 c eye diagram (input = 2ma p-p ) max3864 toc12 80ps/div 50mv/div input = 2 13 -1 prbs with 72 cid v cc = 3.13v at t a = -40 c typical operating characteristics (v cc = 3.3v, t a = +25? and max3864 ev kit source capacitance = 0.85pf, unless otherwise noted). downloaded from: http:///
max3864 detailed description the max3864 transimpedance amplifier is designed for2.5gbps fiber optic applications. as shown in figure 1, the max3864 comprises a transimpedance amplifier, a voltage amplifier, an output buffer, an output filter, and a dc cancellation circuit. transimpedance amplifier the signal current at the input flows into the summingnode of a high-gain amplifier. shunt feedback through r f converts this current to a voltage. schottky diodes clamp the output voltage for large input currents(figure 2). voltage amplifier the voltage amplifier converts single-ended signals todifferential signals and introduces a voltage gain. output buffer the output buffer provides a back-terminated voltageoutput. the buffer is designed to drive a 100 differen- tial load between out+ and out-. the output voltageis divided between internal 50 load resistors and the external load resistor. in the typical operating circuit,this creates a voltage-divider with a ratio of 1/2. the max3864 can also be terminated with higher output impedances, which increases gain and output voltage swings. 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier 4 _______________________________________________________________________________________ typical operating characteristics (continued) v cc = 3.3v, t a = +25? and max3864 ev kit source capacitance = 0.85pf, unless otherwise noted). pin description 200100 0 -100-200 -100 0 -50 50 100 dc transfer function max3864 toc10 input current ( a) differential ouitput voltage (mv p-p ) eye diagram (input = 20 a p-p ) max3864 toc09 80ps/div 10mv/div input = 2 23 -1 prbs pin name function 1v cc supply voltage 2 n.c. no connection 3 in amplifier input 4 filter provides bias voltage for the photodiode through a 750 resistor to v cc . when grounded, this pin disables the dc cancellation amplifier to allow a dc path from in to out+ and out- for testing. 5 gnd ground 6 out- inverting output. current flowing into in causes v out- to decrease. 7 out+ noninverting output. current flowing into in causes v out+ to increase. 8 gnd ground eye diagram (input = 2ma p-p ) max3864 toc08 80ps/div 50mv/div input = 2 23 -1 prbs downloaded from: http:///
for optimum supply-noise rejection, the max3864should be terminated with a differential load. if a single- ended output is required, the unused output should be terminated with 50 to v cc . the max3864 will not drive a dc-coupled, 50 grounded load. output filter the max3864 includes a one-pole lowpass filter thatlimits the circuit bandwidth and improves noise perfor- mance. dc cancellation circuit the dc cancellation circuit uses low-frequency feed-back to remove the dc component of the input signal (figure 3). this feature centers the input signal within the transimpedance amplifier? linear range, thereby reduc- ing pulse-width distortion (pwd) on large input signals. the dc cancellation circuit is internally compensated and therefore does not require external capacitors. this circuit minimizes pwd for data sequences that exhibit a 50% duty cycle and mark density. a duty cycle or mark density significantly different from 50% causes the max3864 to generate pwd. dc cancellation current is drawn from the input and creates noise. for low-level signals with little or no dc component, this is not a problem. amplifier noise will increase for signals with significant dc component (see typical operating characteristics ). max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier _______________________________________________________________________________________ 5 voltage amplifier transimpedance amplifier output buffer output filter out+ 50 50 out- v cc r f = 1k v cc lowpass filter 750 filter in gnd dc cancellation circuit disable max3864 figure 1. functional diagram amplitude output (large signals) time output (small signals) figure 2. limited output amplitude input from photodiode time input (after dc cancellation) figure 3. dc cancellation effect on input downloaded from: http:///
applications information optical power relations many of the max3864 specifications relate to the inputsignal amplitude. when working with fiber optic receivers, the input is usually expressed in terms of average optical power and extinction ratio. figure 4 shows relations that are helpful for converting optical power to input signal when designing with the max3864. optical power relations are shown in table 1; the defini- tions are true if the average duty cycle and mark densi- ty of the input data are 50%. optical sensitivity calculations the max3864 input-referred rms noise current (i n ) generally determines the receiver sensitivity. to obtaina system bit-error rate (ber) of 1e-10, the minimum sig- nal-to-noise ratio (snr) is 12.7. the input sensitivity, expressed in average power, can be estimated as: where is the photodiode responsivity, including fiber- to-photodiode coupling efficiency in a/w and i n in ?. for example, if snr = 12.7, i n = 0.490?, r e = 10, and = 1, then sensitivity is -24dbm. input optical overload the overload is the largest input that the max3864accepts while meeting deterministic jitter specifications. the optical overload can be estimated in terms of aver- age power with the following equation (assumes r e = ): optical linear range the max3864 has high gain, which limits the outputswhen the input signal exceeds 40? p-p . the max3864 operates in a linear range for inputs not exceeding: layout considerations use good high-frequency design and layout techniques. the use of a multilayer circuit board with separate ground and power planes is recommended. connect the gnd pins to the ground plane with the shortest possible traces. noise performance and bandwidth will be adversely affected by capacitance at the in pin. minimize capaci- tance on this pin, and select a low-capacitance photodi- ode. assembling the max3864 in die form using chip and wire technology provides the best possible performance. figure 5 shows the recommended layout for a to header. the so package version of the max3864 is offered as an easy way to characterize the circuit and to become famil- iar with the circuit? operation, but it does not offer opti- mum performance. when using the so version of the max3864, the package capacitance adds approximately 0.3pf at the input. the pc board between the max3864 input and the photodiode also adds parasitic capaci- tance. keep the input line short, and remove power and ground planes beneath it. gnd connect gnd as close to the ac ground of the photode- tector diode as possible. the photodetector ac ground is usually the ground of the filter capacitor from the photode- tector cathode. the total loop (from gnd, through the bypass capacitor and the diode, and back to in) should be no more than approximately 1/5th of a wavelength. overload 10log 2map - p 1000 2 dbm = ?? ? ?? ? sensitivity =10log snr 2 dbm + () () ?? ? ?? ? ir r ne e 1 1 1000 max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier 6 _______________________________________________________________________________________ po pi p avg time power p in figure 4. optical power relations parameter symbol relation average power p ave p ave = (p 0 + p 1 ) / 2 extinction ratio r e r e = p 1 / p 0 optical power of a 1 p 1 p 1 = 2p ave r e / (r e + 1) optical power of a 0 p 0 p 0 = 2p ave / (r e + 1) signal amplitude p in p in = p 1 - p 0 = 2p ave (r e - 1) / (r e + 1) table 1. optical power relations note: assuming a 50% average input duty cycle and mark density. linear range = 10log 4- 2 dbm 0 1 1000 1 + () () ?? ? ?? ? ap p r r e e downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier _______________________________________________________________________________________ 7 in v cc v cc gnd 200 figure 6. equivalent input circuit top view of to-46 header photodiode is mountedon c filt . case is ground. v cc filt in c filt c vcc out+ out- gnd photodiode max3864 figure 5. suggested layout for to-46 header photodiode filter supply voltage noise at the photodiode cathode pro- duces a current i = c pd v / t, which reduces the receiver sensitivity (c pd is the photodiode capaci- tance). the filter resistor of the max3864, combinedwith an external capacitor, can be used to reduce this noise (see the typical application circuit ). current gen- erated by supply noise voltage is divided betweenc filter and c pd . the input noise current due to sup- ply noise is (assuming the filter capacitor is much larg-er than the photodiode capacitance): if the amount of tolerable noise is known, the filter capacitor can be easily selected: for example, with a maximum noise voltage equal to 100mv p-p , c pd = 0.85pf, r filter = 750 , and i noise selected to be 250na (half of the max3864? input noise): wire bonding for high current density and reliable operation, themax3864 uses gold metalization. connections to the die should be made with gold wire only, using ball- bonding. wedge bonding is not recommended. die thickness is typically 15mils (0.375mm). c= 100mv filter () () () ( ) = 085 750 250 453 .pf na pf c= v filter noise () ( ) () () c ri pd filter noise i= v noise noise () ( ) () ( ) c rc pd filter filter downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier 8 _______________________________________________________________________________________ v cc out+out- gnd 50 50 figure 7. equivalent output circuit downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier _______________________________________________________________________________________ 9 30mils 50mils 1.27mm out+ gnd out- gnd v cc input filter (0.762mm) chip information transistor count: 320process: bipolar (silicon germanium) chip topography downloaded from: http:///
max3864 2.5gbps, +3v to +5.5v, wide dynamic range transimpedance preamplifier maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2005 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. soicn .eps package outline, .150" soic 1 1 21-0041 b rev. document control no. approval proprietary information title: top view front view max 0.010 0.069 0.019 0.157 0.010 inches 0.150 0.007 e c dim 0.014 0.004 b a1 min 0.053 a 0.19 3.80 4.00 0.25 millimeters 0.10 0.35 1.35 min 0.49 0.25 max 1.75 0.050 0.016 l 0.40 1.27 0.394 0.386 d d min dim d inches max 9.80 10.00 millimeters min max 16 ac 0.337 0.344 ab 8.75 8.55 14 0.189 0.197 aa 5.00 4.80 8 n ms012 n side view h 0.244 0.228 5.80 6.20 e 0.050 bsc 1.27 bsc c h e e b a1 a d 0 -8 l 1 variations: package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) downloaded from: http:///
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