docsis 3.0 upstream amplifier max3518 _______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. typical application circuit appears at end of data sheet. general description the max3518 is an integrated catv upstream ampli - fier ic designed to meet the docsis 3.0 requirements, while disspating only 1.25w. the amplifier covers a 5mhz to 85mhz input frequency range (275mhz, 3db bandwidth), and is capable of transmitting four qpsk modulated carriers, each at +58dbmv, simultaneously within this range. both input and output ports are dif - ferential, requiring that an external balun be used at the output port. the gain is controlled in 1db steps over a 63db range using a spi? 3-wire interface. the max3518 operates from a single +5v supply. four power codes are provided to allow maximum supply current to be reduced as determined by distortion requirements. in addition, for each power code, sup - ply current is automatically reduced as gain is reduced while maintaining distortion performance. for docsis 3.0 applications, the max3518 draws 300ma at 33db gain, dropping to 250ma at 31db gain. the max3518 supply current drops to 5ma between bursts to minimize power dissipation in transmit-disable mode. control logic levels are 3.3v cmos. the max3518 is available in a 20-pin thin qfn pack - age, and operates over the extended industrial tem - perature range (-40 c to +85 c). applications docsis 3.0 cable modems voip modems set-top boxes features ? +5v supply voltage ? low power: 1.25w at 31db gain, 64dbmv output ? ultra-low 25mw dissipation in transmit-disable mode ? 63db gain control range in 1db steps ? -60dbc harmonic distortion at 64dbmv output ? small 5mm x 5mm thin qfn package ? low burst on/off transient ? 275mhz, 3db bandwidth ordering information max3518 2 3 1 in+ in- n.c.* n.c. n.c. n.c.* v cc sclk note: n.c.* pins must be left unconnected. sda cs txen n.c. n.c. n.c. n.c. v cc out+ out- 13 4 5 14 15 12 11 gnd gnd serial interface 9 1 0 8 7 6 17 16 18 19 20 + denotes a lead(pb)-free/rohs-compliant package. * ep = exposed pad. pin configuration/functional diagram spi is a trademark of motorola, inc. part temp range pin package MAX3518ETP+ -40 c to +85 c 20 tqfn-ep* 19-4390; rev 0; 2/09 evaluation kit available
docsis 3.0 upstream amplifier max3518 2 _______________________________________________________________________________________ stresses beyond those listed under absolute 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. v cc to gnd ........................................................... -0.3v to +5.5v in+, in- ...................................................... -0.3v to (v cc + 0.3v) out+, out- ............................................... -0.3v to (v cc + 3.6v) txen, sda, sclk, cs ......................................... -0.3v to +4.2v rf input power ............................................................... +10dbm continuous power dissipation (t a = +70 c) (note 1) (derate 29mw/ c above t a = +70 c) ...................... 2000mw operating temperature range ......................... -40 c to +85 c junction temperature ...................................................... +150 c storage temperature range ........................... -65 c to +165 c lead temperature (soldering, 10s) ................................. +300 c dc electrical characteristics ( typical application circuit as shown, v cc = 4.75v to 5.25v, v gnd = 0, txen = high, t a = -40 c to +85 c, unless otherwise speci - fied. typical values are at v cc = 5v, t a = +25 c.) (note 2) caution! esd sensitive device absolute maximum ratings note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . parameter symbol conditions min typ max units supply voltage v cc 4.75 5.25 v supply current transmit mode i cc gain code = 63, power code = 3 (33db gain typ) 290 315 ma gain code = 59, power code = 1 (29db gain typ) 160 supply current transmit disable mode i cc txen = low 5 6.5 ma input high voltage v inh 2.0 3.6 v input low voltage v inl 0.7 v input high current i biash 10 a input low current i biash -10 a ac electrical characteristics ( typical application circuit as shown, v cc = 4.75v to 5.25v, v gnd = 0, txen = high, t a = -40 c to +85 c, unless otherwise speci - fied. typical values are at v cc = 5v, t a = +25 c.) (note 2) parameter symbol conditions min typ max units frequency range f in (note 3) 5 85 mhz voltage gain, z in = 200 , z out = 75 , power code = 3 (note 4) a v gain code = 63 32 33 34 db gain code = 53 22 23 24 gain code = 43 12 13 14 gain code = 33 2 3 4 gain code = 23 -8 -7 -6 gain code = 13 -18 -17 -16 gain code = 03 -28 -27 -26 voltage gain variation with power code , a ny gain code 0.1 db gain rolloff voltage gain = -28db to +33db, f in = 5mhz to 85mhz -0.3 db gain step size voltage gain = -28db to +33db, f in = 5mhz to 85mhz 0.7 1.0 1.3 db
docsis 3.0 upstream amplifier max3518 ________________________________________________________________________________________ 3 note 2: min/max values are production tested at t a = +85c. note 3: production tested at 10mhz and 85mhz. note 4: voltage gain does not include loss due to input and output transformers. note 5: guaranteed by design and characterization. ac electrical characteristics (continued) ( typical application circuit as shown, v cc = 4.75v to 5.25v, v gnd = 0, txen = high, t a = -40 c to +85 c, unless otherwise speci - fied. typical values are at v cc = 5v, t a = +25 c.) (note 2) transmit-disable mode noise any bw = 160khz from 5mhz to 85mhz, txen = low, voltage gain = -27db to +33db (note 5) -66 dbmv isolation in transmit-disable mode txen = low 80 db noise figure nf transmit mode, voltage gain = +13db to +33db (note 5) 11 db noise figure slope transmit mode, voltage gain = -27db to +33db -1.0 db/db transmit-disable/transmit- enable transient duration txen input rise/fall time < 0.1s 2 s transmit-disable/transmit- enable transient step size gain = 33db 25 50 mv p-p gain = 4db 1 input impedance z in balanced 200 w input return loss 200 system 15 db output return loss 75 system (note 5) 11 15 db output return loss in transmit-disable mode 75 system, txen = low (note 5) 11 15 db 2nd harmonic distortion hd2 input tone at 33dbmv, v out = +64dbmv, power code = 3 (note 5) -70 -57 dbc 3rd harmonic distortion hd3 input tone at 33dbmv, v out = +64dbmv, power code = 3 (note 5) -60 -56 dbc two-tone 2nd-order distortion im2 input tones at 30dbmv, v out = +61dbmv/tone, power code = 3 (note 5) -70 -57 dbc two-tone 3rd-order distortion im3 input tones at 30dbmv, v out = +61dbmv/tone, power code = 3 (note 5) -60 -54 dbc four tone spurs four input tones at 27dbmv, v out = +58dbmv/tone, power code = 3 -55 dbc output 1db compression point p1db gain = 33db 74 dbmv timing characteristics ( typical application circuit as shown, v cc = 4.75v to 5.25v, v gnd = 0, t a = -40c to +85c, unless otherwise specified. typical values are at v cc = 5v, t a = +25c.) (note 2) parameter symbol conditions min typ max units sen to sck rise set time t sens 20 ns sen to sck rise hold time t senh 10 ns sda to sck setup time t sdas 20 ns sda to sck hold time t sdah 10 ns sck pulse-width high t sclkh 50 ns sck pulse-width low t sclkl 50 ns maximum clk frequency 10 mhz
docsis 3.0 upstream amplifier max3518 4 _______________________________________________________________________________________ typical operating characteristics (max3518 ev kit, v cc = +5v, v in = 33dbmv, f in = 42mhz, z load = 75 ? , t a = +25c, power code = 3, unless otherwise noted.) suppl y current vs. gain code gain code supply current (ma) max3518 toc01 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 0 50 100 150 200 250 300 350 pc = 3 pc = 2 pc = 1 pc = 0 suppl y current vs. tempera ture temperature ( c) supply current (ma) max3518 toc02 -50 0 50 100 295 296 297 298 299 300 301 v cc = +4.75v v cc = +5.00v v cc = +5.25v transmit disable current vs. tempera ture temperature ( c) supply current (ma) max3518 toc03 -50 0 50 100 4.3 4.4 4.5 4.6 4.7 4.8 4.9 5.0 5.1 txen = low vol t age gain vs. tempera ture temperature ( c) voltage gain (db) max3518 toc04 -50 0 50 100 32.0 32.5 33.0 33.5 34.0 v cc = +5.00v v cc = +5.25v v cc = +4.75v vol t age gain vs. tempera ture temperature (c) voltage gain (db) max3518 toc05 -50 0 50 100 32.0 32.5 33.0 33.5 34.0 pc = 3 pc = 1 pc = 2 pc = 0 vol t age gain vs. frequency frequency (mhz) voltage gain (db) max3518 toc06 0 100 200 300 400 500 -40 -30 -20 -10 0 10 20 30 40 gc = 63 gc = 53 gc = 43 gc = 33 gc = 23 gc = 13 gc = 3 vol t age gain vs. gain code gain code voltage gain (db) max3518 toc07 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 -40 -30 -20 -10 0 10 20 30 40 gain step size vs. gain code gain code gain step (db) max3518 toc08 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 noise figure vs. gain code gain code noise figure (db) max3518 toc09 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 0 5 10 15 20 25 30 t a = -40c t a = +25c t a = +85c
docsis 3.0 upstream amplifier max3518 ________________________________________________________________________________________ 5 typical operating characteristics (continued) (max3518 ev kit, v cc = +5v, v in = 33dbmv, f in = 42mhz, z load = 75 ? , t a = +25c, power code = 3, unless otherwise noted.) 2nd harmonic distor tion vs. input frequency frequency (mhz) 2nd harmonic distortion (dbc) max3518 toc10 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 100 -100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50 p out = +64dbmv, p diss = 1.25w t a = -40c t a = +25c t a = +85c 3rd harmonic distor tion vs. input frequency input frequency (mhz) 3rd harmonic distortion (dbc) max3518 toc11 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 100 -70 -68 -66 -64 -62 -60 -58 -56 -54 -52 -50 p out = +64dbmv, p diss = 1.25w t a = -40c t a = +25c t a = +85c im2 vs. input frequency (f 1 + f 2 ) frequency (mhz) im2 (dbc) max3518 toc12 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 100 -100 -95 -90 -85 -80 -75 -70 -65 -60 -55 -50 p out = +61dbmv/tone, p diss = 1.25w 1mhz tone spacing t a = +85c t a = +25c t a = -40c frequency (mhz) im3 (dbc) max3518 toc13 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 100 -70 -68 -66 -64 -62 -60 -58 -56 -54 -52 -50 1mhz tone spacing p out = +61dbmv/tone, p diss = 1.25w im3 vs. input frequency (2f 1 - f 2 ) t a = -40c t a = +25c t a = +85c txen transient vs. gain code gain code txen transient (mv p-p ) max3518 toc14 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 0 5 10 15 20 25 30 35 40 output return loss vs. frequency frequency (mhz) output return loss (db) max3518 toc15 0 2 0 4 0 6 0 8 0 100 120 140 160 180 200 -20 -15 -10 -5 0 t a = -40c t a = +25c t a = +85c output return loss vs. frequency (transmit disable mode) frequency (mhz) output return loss (db) max3518 toc16 0 2 0 4 0 6 0 8 0 100 120 140 160 180 200 -20 -15 -10 -5 0 t a = -40c t a = +25c t a = +85c
docsis 3.0 upstream amplifier max3518 6 _______________________________________________________________________________________ detailed description programmable-gain amplifer the programmable-gain amplifier (pga) provides 63db of output level control in 1db steps. the gain of the pga is determined by a 6-bit gain code (gc5Cgc0) programmed through the serial data interface (tables 1 and 2). specified performance is achieved when the input is driven differentially. four power codes (pc1Cpc0) allow the pga to be used with reduced bias current when distortion performance can be relaxed. in addition, for each power code, bias current is automatically reduced with gain code for maximum efficiency. the pga features a differential class a output stage capable of driving four +58dbmv qpsk modulated signals, or a single +64dbmv qpsk modulated signal into a 75 load. this architecture provides superior even-order distortion performance but requires that a transformer be used to convert to a single-ended out - put. in transmit-disable mode, the output amplifiers are powered down, resulting in low output noise, while maintaining impedance match. 3-wire serial interface (spi) and control registers the max3518 includes two programmable registers for initializing the part and setting the gain and power consumption. the 4 msbs are address bits; the 8 least significant bits (lsbs) are used for register data. data is shifted msb first. note: the registers must be written 100s after the device is powered up, and no earlier. once a new set of register data is clocked in, the corresponding power code and/or gain code does not take effect until txen transitions from high to low. applications information power codes the max3518 is designed to meet the stringent linearity requirements of docsis 3.0 using power code (pc) 3. for docsis 2.0, pc = 1 is recommended, which results in substantial supply current reduction. the full range of gain codes can be used in any power code. the gain difference between power codes is typically less than 0.1db. pin description pin name function 1, 5 gnd ground 2 in+ positive pga input 3 in- negative pga input 4, 11 n.c. no connection. these pins must remain open. 6 sclk serial interface clock 7 sda serial interface data 8 cs serial interface enable 9 txen transmit enable. txen = high places the device in transmit mode. 10 v cc supply voltage for serial interface 12 out- negative output 13, 15, 16, 18, 19, 20 n.c. no connection. connect these pins to ground. 14 out+ positive output 17 v cc supply voltage for programmable-gain amplifier (pga) ep ground table 1. register description register name register address data 8 bits b7 b6 b5 b4 b3 b2 b1 b0 power/gain 0000 pc2 pc1 gc5 gc4 gc3 gc2 gc1 gc0 initialize 0001 0 0 0 0 0 0 0 0
docsis 3.0 upstream amplifier max3518 ________________________________________________________________________________________ 7 transmit disable mode between bursts in a docsis system, the max3518 should be put in transmit-disable mode by setting txen low. the output transient on the cable is kept well below the docsis requirement during the txen transitions. if a gain or power change is required, new values of pc and gc should be clocked in during transmit operation (txen low). the new operating point of the max3518 is set when txen transitions low during the time between bursts. output transformer the max3518 output circuits are open-collector differ - ential amplifiers. on-chip resistors across the collectors provide a nominal output impedance of 75 in transmit mode and transmit-disable mode. to match the output of the max3514/max3516 to a single-ended 75 load, a 1:1 transformer is required. this transformer must have adequate bandwidth to cover the intended appli - cation. note that some rf transformers specify band - width with a 50 source on the primary and a matching table 2. reg 00 gain control figure 1. spi 3-wire interface timing diagram bit name bit location (0 = lsb) recommended default function 7,6,5,4,3,2,1,0 0000 0000 must be programmed to 0000 0000 upon power-up for specified performance. table 3. initialize register d3 a3 a2 a1 a0 d7 d6 d5 d4 d0 d2 d1 sclk cs sda t sens t senh t sdas t sdah t sclkh t sclkl bit name bit location (0 = lsb) recommended default function pc[1:0] 7,6 11 sets the power code, which controls the bias current drawn by the device in transmit mode: 11 - pc = 3, maximum current draw . . . 00 - pc = 0, minimum current draw (see the typical operating characteristics .) gc[5:0] 5,4,3,2,1,0 11 1111 sets the gain code, which determines the voltage gain of the amplifier: 11 1111 - gc = 63, voltage gain = 33db (typ). 11 1110 - gc = 62, voltage gain = 32db (typ). . . . 00 0011 - gc = 03, voltage gain = -27db (typ). (see the ac electrical characteristics .)
docsis 3.0 upstream amplifier max3518 8 _______________________________________________________________________________________ resistance on the secondary winding. operating in a 75 system tends to shift the low-frequency edge of the transformer bandwidth specification up by a factor of 1.5 due to primary inductance. keep this in mind when specifying a transformer. bias to the output stage is provided through the center tap on the transformer primary. this greatly diminishes the on/off transients present at the output when switch - ing between transmit and transmit-disable modes. commercially available transformers typically have adequate balance between half-windings to achieve substantial transient cancellation. finally, keep in mind that transformer core inductance varies with temperature. adequate primary inductance must be present to sustain broadband output capability as temperatures vary. input circuit to achieve rated performance, the inputs of the max3518 must be driven differentially with an appro - priate input level. the differential input impedance is 200 . most applications require an anti-alias filter preceding the device. the filter should be designed to match this 200 ? impedance. the max3518 has sufficient gain to produce an output level of 64dbmv qpsk when driven with a +33dbmv input signal. if an input level greater than +34dbmv is used, the 3rd-order distortion performance will degrade slightly. layout issues a well-designed printed circuit board (pcb) is an essen - tial part of an rf circuit. for best performance, pay attention to power-supply layout issues as well as the output circuit layout. no connect pins pins 4 and 11 must be left open, not connected to sup - ply or ground or any other node in the circuit. pins 13, 15, 16, 18, 19, and 20 should be connected to ground. output circuit layout the differential implementation of the max3518 output has the benefit of significantly reducing even-order distortion, the most significant of which is 2nd-har - monic distortion. the degree of distortion cancellation depends on the amplitude and phase balance of the overall circuit. it is important to keep the trace lengths from the output pins equal. power-supply layout for minimal coupling between different sections of the ic, the ideal power-supply layout is a star configuration. this configuration has a large-value decoupling capaci - tor at the central power-supply node. the power-supply traces branch out from this node, each going to a sepa - rate power-supply node in the circuit. at the end of each of these traces is a decoupling capacitor that provides a very low impedance at the frequency of interest. this arrangement provides local power-supply decoupling at each power-supply pin. the power-supply traces must be capable of carrying the maximum current without significant voltage drop. the output transformer center tap node, vcc_ct, must be connected to supply through a 3 resistor to reduce the supply voltage on out+ and out-. this resistor must be rated to dissipate 250mw at +85c. exposed pad thermal considerations the exposed pad (ep) of the max3518s 20-pin tqfn package provides a low thermal resistance path to the die. it is important that the pcb on which the max3518 is mounted be designed to conduct heat from this con - tact. in addition, the ep should be provided with a low- inductance path to electrical ground. it is recommended that the ep be soldered to a ground plane on the pcb, either directly or through an array of plated via holes. chip information process: sige bicmos
docsis 3.0 upstream amplifier max3518 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 9 ? 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. typical application circuit max3518 in+ in- n.c.* vcc dig vcc_rf vcc_rf vcc_ct vcc_dig v cc sclk sda cs txen n.c. n.c. n.c. n.c. v cc 1:1 vcc_ct n.c. n.c. n.c.* 3 out+ out- gnd gnd output 5v input + ? anti-alias filter note: n.c.* pins must be left unconnected. serial interface 17 16 18 19 20 9 1 0 8 7 6 1 4 5 3 2 15 12 11 13 14 package type package code document no. 20 tqfn-ep t2055-5 21-140 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages .
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