general description the max3660 high-linearity analog rf transimpedance amplifier (tia) is intended for passive optical network (pon) video receiver applications. with 66db maxi- mum variable gain and integrated uptilt, the max3660 provides 23dbmv/channel 1db at 870mhz (19dbmv/channel at 47mhz) for optical inputs between +2dbm to -8dbm (at 4.2% omi) using simple feed-for- ward automatic gain control (agc). it can also be config- ured with feedback agc for even greater dynamic range. cnr is better than 48db from 47mhz to 870mhz (1.0a/w photodiode and -165db/hz rin) at -8dbm with 4.2% omi, or -6dbm with 3.3% omi. cso and ctb are better than -61dbc and -65dbc, respectively. the device supports extended frequency operation to > 1000mhz. the very low true-tia input impedance accommodates a variety of photodiodes, eliminating the need for an input matching network and improving yield. applications ftth optical network termination (ont) features ? pin compatible with max3654 ? operates to > 1000mhz ? 23dbmv/ch output at 870mhz ? 4.5pa/hz 1/2 amplifier ein without photodiode ? 58dbm oip2 ? 24dbm oip3 ? no input matching required ? single +5v supply ? 650mw dissipation ? -40 c to +85 c operating temperature range max3660 analog catv transimpedance amplifier ________________________________________________________________ maxim integrated products 1 15 16 14 13 6 5 7 in+ v cc *the exposed pad must be connected to ground. 8 v cc out+ v cc v cc 12 gnd 4 12 11 9 gnd gnd gnd ep* hyst mute vagc max3660 in- out- 3 10 test thin qfn-ep (4mm ) top view + pin configuration ordering information 19-4223; rev 0; 7/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. + denotes a lead-free/rohs-compliant package. * ep = exposed pad. evaluation kit available typical application circuit appears at end of data sheet. part temp range pin-package MAX3660ETE+ -40 c to +85 c 16 tqfn-ep*
max3660 analog catv transimpedance amplifier 2 _______________________________________________________________________________________ absolute maximum ratings dc electrical characteristics (v cc = +4.75v to +5.25v, t a = -40? to +85?. typical values are at v cc = +5v, t a = +25?, unless otherwise noted.) (note 1) 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 range, v cc........................................ -0.3v to +5.5v in+, in-, vagc, mute , hyst, test..................................(v ee - 0.4v) to (v cc + 0.4v) output current (out+, out-) ............................................60ma maximum voltage (out+, out-) ............................(v cc + 0.4v) continuous power dissipation (t a = +70 c) 16-pin tqfn-ep (derate 16.9mw/ c above +70 c)..1349mw operating temperature range ...........................-40 c to +85 c storage temperature range .............................-55 c to +175 c lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units supply current i cc 130 180 ma gain control input current i vagc v vagc = 1.4v -15 -200 a mute input high v ih 2.0 v mute input low v il 0.5 v mute input current i il , i ih v mute = 0.5v, 2.0v 30 a ac electrical characteristics (v cc = +4.75v to +5.25v, t a = -40? to +85?, output z l = 75 , unless otherwise noted. typical values are at v cc = +5v, t a = +25?, unless otherwise noted.) parameter symbol conditions min typ max units 47mhz to 870mhz 0.9 frequency response flatness (notes 2, 3, 4) 47mhz to 1000mhz 1.0 db 47mhz, v vagc = 0v 66 47mhz, v vagc = 0.175v (note 2) 63.5 66 67.5 47mhz, v vagc = 0.5v (note 2) 54 56.5 58 47mhz, v vagc = 1.4v (note 2) 45.5 48 49.5 transimpedance, differential zt 47mhz, v vagc = 1.6v 46.5 db gain tilt linear, 870mhz vs. 47mhz (note 4) 3.8 4.5 5.0 db gain control stability 0.175v v vagc 1.4v, r hyst = open (notes 2, 5) 0.8 2.0 db output second-order intercept oip2 47mhz to 870mhz, 0.175v v vagc 1.4v (note 6) 58 dbm output third-order intercept oip3 47mhz to 870mhz, 0.175v v vagc 1.4v (note 6) 20 24 dbm
max3660 analog catv transimpedance amplifier _______________________________________________________________________________________ 3 note 1: dc parameters are tested at t a = +25? and +85?. note 2: guaranteed by design and characterization. note 3: frequency response flatness is the maximum difference between the frequency response at any point and a line connect- ing the end points of 47mhz and 870mhz. note 4: measured using the max3660 ev kit circuit in figure 4 with an excelight sxt5241-q/gpa triplexer (8mm photodiode lead length). note 5: gain control stability is the maximum variation in transimpedance (over process, voltage, and temperature) for any valid vagc voltage. note 6: oip2 and oip3 values are tested with tones at 800mhz and 850mhz. note 7: hysteresis is referred to optical gain, equivalent to two times electrical gain (db). note 8: not including balun. ac electrical characteristics (continued) (v cc = +4.75v to +5.25v, t a = -40? to +85?, output z l = 75 , unless otherwise noted. typical values are at v cc = +5v, t a = +25?, unless otherwise noted.) parameter symbol conditions min typ max units equivalent input noise, including photodiode ein 47mhz to 870mhz, 0.175v v vagc 1.4v (notes 2, 4) 5.5 7.3 pa/hz 1/2 r hyst = open 0.14 gain control hysteresis (notes 1, 7) r hyst = gnd 0.75 db (optical) transimpedance, mute v mute 0.8v, 47mhz 20 db rf output return loss -s22 47mhz to 870mhz (notes 4, 8) 20 db 0.5pf 0.5pf 0.5pf 5 to tia 5 1nh 1nh 5nh 5nh 0.3pf 0.3pf out+/- in+/- mute 48db to 54db 54db to 60db 60db to 66db vagc hyst tia max3660 v cc figure 1. photodiode and header model figure 2. functional diagram
max3660 analog catv transimpedance amplifier 4 _______________________________________________________________________________________ typical operating characteristics (v cc = +5.0v, t a = +25 c, unless otherwise noted. cnr, cso, and ctb are for the max3660 ev kit at p in = -8dbm, with channels above 350mhz attenuated 6db.) gain (zt) vs. frequency (v vagc = 0.10v, 0.175v, 0.25v, 0.35v, 0.7v, 1.05v, 1.4v, 1.6v; t a = -40 c, +25 c, +85 c) max3660 toc01 frequency (mhz) gain (zt) (db ) 1400 1600 1200 200 600 800 1000 400 45 50 55 60 65 70 75 80 40 0 v vagc = 0.1v v vagc = 1.6v gain (zt) vs. vagc (t a = -40 c, +25 c, +85 c) max3660 toc02 vagc (v) gain (zt) (db ) 1 45 50 55 60 65 70 75 40 0.1 10 f = 875mhz f = 47mhz deviation from linear tilt vs. frequency (v vagc = 0 to 1.6v; t a = -40 c, +25 c, +85 c) max3660 toc03 frequency (mhz) deviation (db) 800 600 200 400 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0 1000 t a = -40 c t a = +25 c t a = +85 c deviation from ideal gain vs. vagc (frequency = 47mhz, t a = -40 c, +25 c, +85 c) max3660 toc04 vagc (v) deviation from gain (db) 1.2 0.8 0.4 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0 1.6 t a = -40 c t a = +25 c t a = +85 c oip2, oip3 vs. vagc max3660 toc05 vagc (v) oip2, oip3 (dbm) 1.5 1.0 0.5 30 40 50 60 70 80 20 0 2.0 oip2 oip3 equivalent input noise vs. frequency max3660 toc06 frequency (mhz) noise (pa/h 1/2 ) 800 700 500 600 200 300 400 100 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 5.0 0 900 t a = -40 c t a = +25 c t a = +85 c cnr vs. frequency (110 channels, omi = 4.2%/2.1%) max3660 toc07 frequency (mhz) cnr (db) 900 800 700 600 500 400 300 200 100 45 50 55 60 40 0 1000 p in = +2dbm p in = -2dbm p in = -2dbm p in = -6dbm p in = -6dbm p in = -8dbm p in = -8dbm p in = +2dbm cso, ctb vs. frequency (110 channels, p in = +2dbm, omi = 4.2%/2.1%) max3660 toc08 frequency (mhz) cso, ctb (dbc) 800 600 400 200 -75 -70 -65 -60 -55 -50 -80 0 1000 cso ctb cs ctb s22 normalized to 75 max3660 toc09 frequency (mhz) s22 (db) 800 600 400 200 -30 -25 -20 -15 -10 -5 0 -35 0 1000 dut and balun dut only
max3660 analog catv transimpedance amplifier _______________________________________________________________________________________ 5 pin description pin name function 1, 4, 9, 12 v cc +5.0v supply 2 in+ positive analog input. connect to photodiode cathode. 3 in- negative analog input. connect to photodiode anode. 5 vagc agc control input. see the gain (zt) vs. frequency graph. 6 mute active-low mute control input. v mute < 0.8v to disable output. 7 hyst agc hysteresis control input. a resistor from hyst to gnd controls the hysteresis level. 8, 14, 15, 16 gnd supply ground 10 out- negative rf output 11 out+ positive rf output 13 test reserved for test. connect to gnd for normal operation. ep exposed pad. the exposed pad must be soldered to the circuit board ground for proper thermal and electrical performance. detailed description the max3660 variable gain tia has differential ac- coupled photocurrent inputs and 75 differential rf output. when used with a low-cost operational amplifi- er, photodiode assembly, bias network, and balun, the max3660 provides a complete high-performance bpon/gpon video receiver with a simple and effective feed-forward agc. it can also be used with feedback agc. low-noise variable-gain amplifier the low-noise differential input is designed to be ac- coupled to the anode and cathode of the analog photo- diode in a pon triplexer. the maximum input current to achieve rated linearity is 1.675ma p-p . very low tia input impedance provides excellent fre- quency response with no (internal or external) compen- sation between photodiode and amplifier, thus simplifying design, manufacturing, and photodiode selection. vagc and hysteresis control the overall transimpedance is controlled using the vagc input pin. see the typical operating characteristics for descriptions of the transimpedance, oip2 (cso), and oip3 (ctb) performance for vagc voltages between 0 and 1.8v. the max3660 has a very flat and stable gain vs. volt- age characteristic in the range 0.175v v vagc 1.4v, enabling a simple feed-forward agc based on average optical power level as measured by the photodiode dc current (see figure 4 for the ev kit schematic). feedback agc can be used to achieve a wider dynamic range, in which case the vagc voltage would be controlled by an external power detector, such as the max2014, typically through a microcontroller inter- face. in this case, the maximum voltage at vagc should be kept below approximately 1.65v to maintain adequate linearity levels for typical gpon applications. the forward signal path is implemented with three switched variable gain stages, each covering one-third of the total dynamic range. when the voltage input at vagc crosses the points on the gain (zt) vs. vagc curve where a new stage is selected (v vagc = 350mv and v vagc = 700mv), there can be a small (approxi- mately 50ns) deviation in the output, causing an inter- ruption to the catv signal. hysteresis is provided for the vagc input to prevent the output signal from dither- ing when the average optical input level is very close to one of these two switching points. the amount of hys- teresis can be controlled by the value of r hyst , and is minimum (0.14db) when r hyst is open. rf output and cable tilt compensation the max3660 includes integrated cable compensation (uptilt). with a photodiode assembly similar to that described in figure 1, the output at 870mhz is 4db higher compared to the output at 47mhz. about half of the uptilt is due to the combination of photodiode capacitance and the inductance of the triplexer leads, and half is internal to the max3660.
max3660 rf output and input stage the differential outputs should be connected to a balun transformer to produce a single-ended 75 out- put. if the max3660 is used to drive a single-ended postamplifier, the use of a balun is recommended (refer to maxim reference design hfrd-22.4) to achieve adequate linearity and noise performance. with a typical low-cost balun, output return loss (-s22) is better than 15db up to 550mhz and is limited by the balun performance. when mute is logic-low, the transimpedance is less than 20db . applications information photodiode/tia interface the max3660 is designed to provide a 23dbmv/chan- nel output at 870mhz with excellent cso, ctb, and cnr, and its frequency response extends well beyond 1000mhz. the rf output has 4db 1db of uptilt and 0.9db of flatness (47mhz to 870mhz) when used with a photodi- ode and assembly having characteristics similar to those shown in figure 1, which is consistent with a typi- cal low-cost ftth triplexer connected by 5mm leads to matched vias. the max3660? very low input imped- ance (approximately 10 ) also provides tolerance to variations in photodiode and assembly electrical char- acteristics. it is particularly important to provide electrical symme- try in the anode and cathode connections, including the triplexer/rosa lead routing and pcb mounting con- figuration. consult the ev kit and maxim reference designs for examples of good layout techniques. with typical optical transmitter characteristics, the max3660 achieves cso and ctb better than -65dbc and achieves cnr (including amplifier noise, photodiode shot noise, and transmitter rin) of 48db (at -6dbm or greater with omi = 3.3%, or at -8dbm or greater with omi = 4.2%) between 47mhz and 870mhz. refer to the max3660 ev kit data sheet for a description of the setup used for cso, ctb, and cnr typical operating characteristics measurements. to achieve optimum cnr performance, the agc should be configured so that the max3660? gain is greatest (v vagc 0.175v) at the lowest intended optical input level, typically -6dbm or -8dbm. to maintain ctb and cso performance, care should also be exercised when designing the agc so that the maximum operating vagc level is limited to approximately 1.6v. operating with input signal levels greater than 1.6ma p-p can result in a reduction in linearity due to clipping. photodiode bias network a combination of resistors and inductors, such as shown in figure 3, provides dc bias to the photodi- ode. the series connection of two inductors and one resistor is intended to mitigate effects of inductor self- resonance. the dc voltage drop across the lower resistor provides an effective means to measure average optical power for use as a signal strength indicator and/or feed-for- ward agc. the value of the resistors can be adjusted to vary the feed-forward gain. depending on the specific photodi- ode characteristics and desired frequency response, between 5v and 12v should normally be used for v pd . analog catv transimpedance amplifier 6 _______________________________________________________________________________________ tia in+ tia in- v mon 1k 1k 1.8k bead 10 h 10 h 1.8k bead 0.001 f 0.001 f v pd 0.1 f figure 3. photodiode bias network
gain vs. vagc voltage the overall transimpedance at 47mhz is related to the voltage at vagc by the relation: the gain at 870mhz is 4db greater (70db at v vagc = 0.175v) because of the uptilt, although the amount of uptilt can be modified as described above. between 0 and 0.175v the gain is constant, and above 1.5v it falls off relatively quickly. operation above v vagc = 1.6v should be avoided to obtain adequate linearity performance. the high-impedance vagc input should be driven by a source (op amp, dac, etc.) capable of sinking up to 200?. feed-forward agc with a feed-forward circuit like that of the ev kit, the max3660 provides a constant ( 1db) output of 19dbmv/channel at 47mhz and 23dbmv/channel at 870mhz, for optical input levels ranging between -8dbm and +2dbm at omi = 4.2%. feedback agc the vagc voltage can also be controlled from a power detector, such as the max2014 or max9933, for feed- back agc. it is important to note that the gain (zt) vs. vagc char- acteristic includes hysteresis at the two points where the input stage switches gain (350mv and 700mv), which can cause problems such as limit-cycle oscilla- tion with continuous analog feedback implementations. the feedback circuit should be designed to avoid oscil- lation or dithering. uptilt the integrated uptilt results in equal input levels pro- ducing an output voltage that is 4db greater at 870mhz compared to 47mhz, eliminating the loss normally associated with an external passive tilt network. the amount of uptilt can be varied by adjusting the triplexer lead length, or by adding small inductors in series with the anode and cathode, to compensate for photodi- odes/triplexers that differ significantly from figure 1. equivalent input noise the typical equivalent input referred noise (ein) of the max3660 with a photodiode connected at the input is 5.5pa/hz 1/2 , yielding 48db or better cnr under normal bpon/gpon conditions. without a photodiode con- nected, the typical ein is 4.5pa/hz 1/2 . rf output the rf output should be connected to the max3660 using ac-coupling capacitors and a balun transformer to achieve the desired noise and linearity performance. without the capacitors, shorting out+ and out- together, or shorting out+ or out- to ground, can draw sufficient current to damage the output stage. ev kit circuit the max3660 ev kit circuit shown in figure 4 was used to collect the data in the typical operating characteristics figures. when connected to a photodi- ode-equipped triplexer, the ev kit circuit provides a complete receiver, including photodiode bias, feed-for- ward agc, and output transformer. jumper ju1 controls the mute input, ju3 sets the amount of hysteresis, and ju2 controls the input of the op amp driving the vagc input. install ju2 to enable feed-forward vagc, or alternatively, the gain can be controlled by tp6 with ju2 removed. zt db db mv vmv vagc () log , ? =+ () ? ? ? ? ? ? ? ? 66 20 175 0. .. 175 1 4 vv v vagc ? () max3660 analog catv transimpedance amplifier _______________________________________________________________________________________ 7
max3660 analog catv transimpedance amplifier 8 _______________________________________________________________________________________ ep max3660 u1 tp2 tp3 tp5 1 v cc 2 in+ 12 v cc 11 out+ 5 vagc 6 mute 16 gnd 15 gnd 14 gnd 13 test vcc c7 0.1 f 4 v cc vcc vcc c8 0.1 f c1 0.001 f vcc vpd vcc gnd c8 0.1 f c14 33 f 9 v cc vcc c9 0.1 f u8 cx2038 j2 c4 0.001 f 10 out- c5 0.001 f 3 in- c2 0.001 f r21 1k r1 1k l5 1.8k bead r3 100k l6 10 h l2 10 h l1 1.8k bead u5 vpd c3 0.1 f c6 1 f c10 1 f r22 open jp2 r4 100k tp6 tp4 r5 100k c11 1 f u2 7 hyst 8 gnd jp1 r6 1k r7 open r8 1k jp3 r9 20k tp1 tp13 vcc vpd c13 33 f figure 4. max3660 ev kit schematic
max3660 analog catv transimpedance amplifier 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 _____________________ 9 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. chip information process: sige bipolar substrate: soi out+ -8dbm to +2dbm, -6dbm to +2dbm 0.001 f 0.001 f 0.001 f 0.001 f out- in+ in- mute 75 cx2038 vagc +5v +5v hyst max3660 gnd ep test 100k 100k 1 f r hyst 1k 1k 1.8k bead 10 h 10 h 1.8k bead v cc v pd 0.1 f typical application circuit package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 16 tqfn-ep t1644+3 21-0139
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