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general description the MAX3983 is a quad copper-cable signal conditioner that operates from 2.5gbps to 3.2gbps. it provides com- pensation for 4x copper infiniband and 10gbase-cx4 ethernet links, allowing spans of 20m with 24awg and 15m with 28awg. the cable driver section provides four selectable preemphasis levels. the input to the cable driver compensates for up to 0.5m of fr4 circuit board material. the cable receiver section provides additional fixed input equalization while offering selectable preem- phasis to drive fr4 circuit boards up to 0.5m. the MAX3983 also features signal detection on all eight inputs and internal loopback that allows for diagnostic testing. it is packaged in a 10mm x 10mm, 68-pin qfn and operates from 0? to +85?. applications 4x infiniband (4 x 2.5gbps) 10gbase-cx4 ethernet (4 x 3.125gbps) 10g fibre channel xaui (4 x 3.1875gbps) 4x copper-cable or backplane transmission (1gbps to 3.2gbps) features link features span 20m with 24awg, 15m with 28awg span 0.5m of fr4 on each host 1.6w total power with 3.3v supply loopback function cable driver features selectable output preemphasis fr4 input equalization signal detect for each channel output disable cable receiver features selectable fr4 output preemphasis cable input equalization signal detect for each channel output disable MAX3983 quad copper-cable signal conditioner ________________________________________________________________ maxim integrated products 1 MAX3983 rx_sd1 rx_sd2 rx_sd3 rx_sd4 tx_sd1 tx_sd2 tx_sd3 tx_sd4 tx_out1 tx_out2 tx_out3 tx_out4 rx_in1 rx_in2 rx_in3 rx_in4 tx_in1 tx_in2 tx_in3 tx_in4 rx_out1 rx_out2 rx_out3 rx_out4 4.7k ? 4.7k ? 3v to 5.5v 3v to 5.5v to host tx_enable rx_enable tx_pe0 rx_pe tx_pe1 serdes tx rx 0.5m v cc [1:4] 3.3v gnd por loopback to host 0.01 f 0.01 f to MAX3983 4x copper cable assembly 20m (24awg) 15m (28awg) v cc or gnd c por typical application circuit ordering information 19-2928; rev 0; 7/03 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. part temp range pin- package pkg code MAX3983ugk 0 c to +85 c 68 qfn g6800-4 pin configuration appears at end of data sheet.
MAX3983 quad copper-cable signal conditioner 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +3.0v to +3.6v, t a = 0 c to +85 c. typical values are at v cc = +3.3v and t a = +25 c, unless otherwise noted.) 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 +6.0v continuous cml output current at tx_out[1:4] , rx_out[1:4] .......................... . 25ma voltage at tx_in[1:4] , rx_in[1:4] , rx_sd[1:4], tx_sd[1:4], rx_enable, tx_enable, rx_pe, tx_pe[0:1], loopback, por (with series resistor 4.7k ? )...................-0.5v to (v cc + 0.5v) continuous power dissipation (t a = +85 c) 68-pin qfn (derate 41.7mw/ c above +85 c) .2.7w operating junction temperature range (t j ) ....-55 c to +150 c storage ambient temperature range (t s ) .......-55 c to +150 c parameter symbol conditions min typ max units rx_en = v cc , tx_en = 0v 360 430 rx_en = 0v, tx_en = v cc 365 430 supply current rx_en = v cc , tx_en = v cc 495 580 ma operating conditions supply voltage v cc 3.0 3.3 3.6 v supply noise tolerance 1mhz f < 2ghz 40 mv p-p operating ambient temperature t a 02585 c bit rate nrz data (note 1) 2.5 3.2 gbps cid consecutive identical digits (bits) 10 bits status outputs: rx_sd[1:4], tx_sd[1:4] signal detect asserted 0 25 a signal detect unasserted v ol 0.4v with 4.7k ? pullup resistor 1.0 1.11 ma signal-detect open-collector current sink v cc = 0v, pullup supply = 5.5v, external pullup resistor 4.7k ? 025a signal-detect response time time from rx_in[1:4] or tx_in[1:4] dropping below 85mv p-p or rising above 175mv p-p to 50% point of signal detect 0.35 s signal-detect transition time rise time or fall time (10% to 90%) 200 ns power-on reset delay 1f capacitor on por to gnd 6 ms control inputs: rx_enable, tx_enable, rx_pe, tx_pe0, tx_pe1, loopback voltage, logic high v ih 1.5 v voltage, logic low v il 0.5 v current, logic high i ih v ih = v cc -150 +150 a current, logic low i il v il = 0v -150 +150 a
MAX3983 quad copper-cable signal conditioner _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = +3.0v to +3.6v, t a = 0 c to +85 c. typical values are at v cc = +3.3v and t a = +25 c, unless otherwise noted.) parameter symbol conditions min typ max units tx section (cable driver) pc board input swing measured differentially at the signal source (note 1) 800 1600 mv p-p input resistance tx_in[1:4]+ to tx_in[1:4]-, differential 85 100 115 ? input return loss 100mhz to 2ghz (note 1) 10 17 db tx_enable = high (notes 1, 2) 1300 1500 1600 output swing tx_enable = low 30 mv p-p output resistance tx_out[1:4]+ or tx_out[1:4]- to v cc , single ended 42 50 58 ? output return loss 100mhz to 2ghz (note 1) 10 13 db output transition time t r , t f 20% to 80% (notes 1, 3) 80 ps random jitter (notes 1, 3) 1.6 ps rms tx_pe1 tx_pe0 00 3 01 6 10 9 output preemphasis see figure 1 11 12 db source to tx_in tx_out to load tx_pe1 tx_pe0 1m, 28awg 0 0 5m, 28awg 0 1 10m, 24awg 1 0 residual output deterministic jitter at 2.5gbps (notes 1, 4, 5) 6-mil fr4 20in 15m, 24awg 1 1 0.10 0.15 ui p-p source to tx_in tx_out to load tx_pe1 tx_pe0 1m, 28awg 0 0 5m, 28awg 0 1 10m, 24awg 1 0 residual output deterministic jitter at 3.2gbps (notes 1, 4, 5) 6-mil fr4 20in 15m, 24awg 1 1 0.15 0.20 ui p-p signal-detect assert level tx_in for tx_sd = high (note 6) 800 mv p-p signal-detect off tx_in for tx_sd = low (note 6) 200 mv p-p rx section (cable receiver) cable input swing measured differentially at the signal source (note 1) 1000 1600 mv p-p input vertical eye opening measured differentially at the input of the MAX3983 (note 1) 175 1600 mv p-p input resistance rx_in[1:4]+ to rx_in[1:4]-, differential 85 100 115 ? input return loss 100mhz to 2ghz (note 1) 10 18 db
MAX3983 quad copper-cable signal conditioner 4 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = +3.0v to +3.6v, t a = 0 c to +85 c. typical values are at v cc = +3.3v and t a = +25 c, unless otherwise noted.) parameter symbol conditions min typ max units rx_enable = high (notes 1, 7) 1100 1500 output swing rx_enable = low 30 mv p-p output resistance rx_out[1:4]+ or rx_out[1:4]- to v cc , single ended 42 50 58 ? output return loss 100mhz to 2ghz (note 1) 10 15 db output transition time t r , t f 20% to 80% (notes 1, 8) 45 80 ps random jitter (notes 1, 8) 1.6 ps rms rx_pe = low 3 output preemphasis rx_pe = high 6 db source to rx_in rx_out to load rx_pe 0in, 6-mil fr4 0 residual output deterministic jitter at 2.5gbps (notes 1, 5, 9, 10) 5m, 28awg ib cable assembly without preemphasis 20in, 6-mil fr4 1 0.10 0.15 ui p-p source to rx_in rx_out to load rx_pe 0in, 6-mil fr4 0 residual output deterministic jitter at 3.2gbps (notes 1, 5, 9, 10) 5m, 28awg ib cable assembly without preemphasis 20in, 6-mil fr4 1 0.15 0.20 ui p-p signal-detect assert level rx_in for rx_sd = high (note 11) 175 mv p-p signal-detect off rx_in for rx_sd = low (note 11) 85 mv p-p end-to-end jitter (tx and rx combined performance) source to tx_in tx_out to rx_in tx_pe1 tx_pe0 rx_out to load rx_pe 1m, 24awg 0 0 0in 0 15m, 24awg 1 1 20in 1 0.15 0.20 residual output deterministic jitter at 2.5gbps (notes 1, 12, 13, 14) 6-mil fr4 20in 20m, 24awg 1 1 20in 1 0.2 0.25 ui p-p
MAX3983 quad copper-cable signal conditioner _______________________________________________________________________________________ 5 electrical characteristics (continued) (v cc = +3.0v to +3.6v, t a = 0 c to +85 c. typical values are at v cc = +3.3v and t a = +25 c, unless otherwise noted.) parameter symbol conditions min typ max units source to tx_in tx_out to rx_in tx_pe1 tx_pe0 rx_out to load rx_pe 1m, 24awg 0 0 5in 0 15m, 24awg 1 1 20in 1 0.20 0.25 residual output deterministic jitter at 3.2gbps (notes 1, 12, 13, 14) 6-mil fr4 20 in 20m, 24awg 1 1 20in 1 0.25 0.3 ui p-p note 1: guaranteed by design and characterization. note 2: measured with 2in of fr4 through infiniband connector with tx_pe1 = tx_pe0 =1. note 3: measured at the chip using 0000011111 or equivalent pattern. tx_pe1 = tx_pe0 = 0 for minimum preemphasis. note 4: all channels under test are not transmitting during test. channel tested with xaui cjpat, as well as this pattern: 19 zeros, 1, 10 zeros, 1010101010 (d21.5 character), 1100000101 (k28.5+ character), 19 ones, 0, 10 ones, 0101010101 (d10.2 character), 0011111010 (k28.5- character). note 5: cables are unequalized, amphenol spectra-strip 24awg and 28awg or equivalent equipped with fujitsu microgiga connector or equivalent. all other channels are quiet. residual deterministic jitter is the difference between the source jit- ter and the output jitter at the load. the deterministic jitter (dj) at the output of the transmission line must be from media- induced loss and not from clock-source modulation. depending upon the system environment, better results can be achieved by selecting different preemphasis levels. note 6: tested with a 1ghz sine wave applied at tx_in under test with less than 5in of fr4. note 7: measured with 3in of fr4 with rx_pe = 1. note 8: measured at the chip using 0000011111 or equivalent pattern. rx_pe = low (minimum). signal source is 1v p-p with 5m, 28awg infiniband cable. note 9: all other receive channels are quiet. tx_enable = 0. channel tested with xaui cjpat as well as this pattern: 19 zeros, 1, 10 zeros, 1010101010 (d21.5 character), 1100000101 (k28.5+ character), 19 ones, 0, 10 ones, 0101010101 (d10.2 character), 0011111010 (k28.5- character). note 10: fr4 board material: 6-mil-wide, 100 ? , edge-coupled stripline (tan = 0.022, 4.0 < r < 4.4). note 11: tested with a 1ghz sine wave applied at rx_in under test with less than 5in of fr4. note 12: channel tested with xaui cjpat as well as this pattern: 19 zeros, 1, 10 zeros, 1010101010 (d21.5 character), 1100000101 (k28.5+ character), 19 ones, 0, 10 ones, 0101010101 (d10.2 character), 0011111010 (k28.5- character). note 13: cables are unequalized, amphenol spectra-strip 24awg or equivalent equipped with fujitsu microgiga connector or equivalent. residual deterministic jitter is the difference between the source jitter at point a and the load jitter at point b in figure 2. the deterministic jitter (dj) at the output of the transmission line must be from media-induced loss and not from clock-source modulation. depending upon the system environment, better results can be achieved by selecting different preemphasis levels. note 14: valid with pattern generator deterministic jitter as high as 0.17ui p-p .
MAX3983 quad copper-cable signal conditioner 6 _______________________________________________________________________________________ pe = 12db pe = 3db v eye = 0.375v p-p v eye = 1.06v p-p differential output = 1.5v p-p figure 1. illustration of tx preemphasis in db MAX3983 MAX3983 signal source 1in l 20in 6 mils 1in l 3in pc board (fr4) a b oscilloscope or error detector sma connectors fujitsu microgiga connectors infiniband cable assembly rx_out rx_in 6 mils 6 mils 6 mils tx_in tx_out 1in l 20in 1in l 3in end-to-end testing fr4 4.0 r 4.4 tan = 0.022 figure 2. end-to-end test setup. the points labeled a and b are referenced for ac parameter test conditions.
MAX3983 quad copper-cable signal conditioner _______________________________________________________________________________________ 7 typical operating characteristics (v cc = +3.3v, t a = +25 c, unless otherwise noted.) transient repsonse MAX3983 toc01 v out a = 3db, tx_pe = 00 b = 6db, tx_pe = 01 c = 9db, tx_pe = 10 d = 12db, tx_pe = 11 a b c d a b c d 3.125gbps k28.7 pattern measured directly at part vertical eye opening vs. cable length MAX3983 toc02 cable length (m) vertical eye opening (mv p-p ) 15 10 5 100 200 300 400 500 600 700 800 900 1000 0 020 tx_pe[1,0] = 00 tx_pe[1,0] = 01 tx_pe[1,0] = 10 tx_pe[1,0] = 11 2.5gbps xaui cjpat 24awg cable cable length (m) dj (ps) 15 10 5 50 100 150 200 250 300 350 0 020 end-to-end deterministic jitter vs. cable length MAX3983 toc03 2.5gbps xaui cjpat all channels transmitting 10in fr4 at tx_in 10in fr4 at rx_out source dj = 23ps a, b c e d a b d c a = 24awg, tx_pe[1,0] = 00 b = 24awg, tx_pe[1,0] = 01 c = 24awg, tx_pe[1,0] = 10 d = 24awg, tx_pe[1,0] = 11 e = 28awg, tx_pe[1,0] = 11 10m 24awg unequalized cable assembly output without MAX3983 MAX3983 toc04 1500mv p-p at transmitter 3.125gbps xaui cjpat cable only 60ps/div 10m 24awg unequalized cable assembly output with MAX3983 preemphasis MAX3983 toc05 3.125gbps xaui cjpat preemphasis, tx_pe[1, 0] = 10 320mv p-p 60ps/div tx_in input return loss vs. frequency MAX3983 toc06 frequency (ghz) differential s11 (db) 3.6 3.2 2.4 2.8 0.8 1.2 1.6 2.0 0.4 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 -50 04.0 using agilent 8720es and atn microwave atn-4112a s-parameter test set de-embedding sma connector, coupling capacitor, and 3in trace
MAX3983 quad copper-cable signal conditioner 8 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = +3.3v, t a = +25 c, unless otherwise noted.) rx_out output return loss vs. frequency MAX3983 toc09 frequency (ghz) differential s22 (db) 3.6 3.2 2.4 2.8 0.8 1.2 1.6 2.0 0.4 -40 -35 -30 -25 -20 -15 -10 -5 0 04.0 using agilent 8720es and atn microwave atn-4112a s-parameter test set de-embedding sma connector, coupling capacitor, and 3in trace power-on reset delay with supply ramp MAX3983 toc12 2ms/div 1v/div 200ma/div v cc i cc 1 f capacitor from por pin to ground tx_out output return loss vs. frequency MAX3983 toc07 frequency (ghz) differential s22 (db) 3.6 3.2 2.4 2.8 0.8 1.2 1.6 2.0 0.4 -35 -30 -25 -20 -15 -10 -5 0 04.0 using agilent 8720es and atn microwave atn-4112a s-parameter test set de-embedding sma connector, coupling capacitor, and 3in trace rx_in input return loss vs. frequency MAX3983 toc08 frequency (ghz) differential s11 (db) 3.6 3.2 2.4 2.8 0.8 1.2 1.6 2.0 0.4 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 -50 04.0 using agilent 8720es and atn microwave atn-4112a s-parameter test set de-embedding sma connector, coupling capacitor, and 3in trace
MAX3983 quad copper-cable signal conditioner _______________________________________________________________________________________ 9 pin description pin name function 1, 2, 16, 17 tx_sd1 to tx_sd4 pc board receiver signal detect, ttl output. this output is open-collector ttl, and therefore requires an external 4.7k ? to 10k ? pullup resistor to v cc . these outputs sink current when the input signal level is not valid. 3, 15 v cc 1 power-supply connection for tx inputs. connect to +3.3v. 4, 7, 10, 13 tx_in1- to tx_in4- pc board receiver negative data inputs, cml. these inputs are internally differentially terminated to the corresponding tx_in+ with 100 ? . 5, 8, 11, 14 tx_in1+ to tx_in4+ pc board receiver positive data inputs, cml. these inputs are internally differentially terminated to the corresponding tx_in- with 100 ? . 6, 9, 12, 40, 43, 46 gnd circuit ground 18 tx_enable cable transmitter enable input, lvttl with 40k ? internal pullup. this pin enables all four cable transmitter outputs tx_out[1:4]. when low, differential output is less than 30mv p-p . set high or open for normal operation. 19 n.c. no connection. do not connect this pin. 20, 23, 26, 29, 32 v cc 2 power-supply connection for tx outputs. connect to +3.3v. 21, 24, 27, 30 tx_out1+ to tx_out4+ cable transmitter positive data outputs, cml. these outputs are terminated with 50 ? to v cc 2. 22, 25, 28, 31 tx_out1- to tx_out4- cable transmitter negative data outputs, cml. these outputs are terminated with 50 ? to v cc 2. 33 tx_pe0 cable transmitter preemphasis control input, lvttl with 40k ? internal pullup. this pin is the least significant bit of the 2-bit preemphasis control. set high or open to assert this bit. 34 tx_pe1 cable transmitter preemphasis control input, lvttl with 40k ? internal pullup. this pin is the most significant bit of the 2-bit preemphasis control. set high or open to assert this bit. 35, 36, 50, 51 rx_sd4 to rx_sd1 cable receiver signal detect, ttl output. this output is open-collector ttl, and therefore it requires an external 4.7k ? to 10k ? pullup resistor to v cc . these outputs sink current when the input signal level is not valid. 37, 49 v cc 3 power-supply connection for rx inputs. connect to +3.3v. 38, 41, 44, 47 rx_in4- to rx_in1- cable receiver negative data inputs, cml. these inputs are internally differentially terminated to the corresponding rx_in+ with 100 ? . 39, 42, 45, 48 rx_in4+ to rx_in1+ cable receiver positive data inputs, cml. these inputs are internally differentially terminated to the corresponding rx_in- with 100 ? . 52 rx_enable pc board transmitter enable input, lvttl with 40k ? internal pullup. this pin enables all four pc board transmitter outputs rx_out[1:4]. when low, differential output is less than 30mv p-p . set high or open for normal operation. 53 por power-on reset connection. connect external capacitor 0.1f c por 10f to ground. see the detailed description . 54, 57, 60, 63, 66 v cc 4 power-supply connection for rx outputs. connect to +3.3v.
MAX3983 quad copper-cable signal conditioner 10 ______________________________________________________________________________________ pin description (continued) pin name function 55, 58, 61, 64 rx_out4+ to rx_out1+ pc board transmitter positive data outputs, cml. these outputs are terminated with 50 ? to v cc 4. 56, 59, 62, 65 rx_out4- to rx_out1- pc board transmitter negative data outputs, cml. these outputs are terminated with 50 ? to v cc 4. 67 rx_pe pc board transmitter preemphasis control input, lvttl with 40k ? internal pullup. set high or open to assert this bit. 68 loopback loopback enable input, lvttl with 40k ? internal pullup. set low for normal operation. set high or open for internal connection of tx_in to rx_out. tx_out continues to transmit when loopback is enabled. ep exposed pad exposed pad. signal and supply ground. for optimal high-frequency performance and thermal conductivity, this pad must be soldered to the circuit board ground. tx_out[1:4]+ tx_out[1:4]- gnd 2 rx_in[1:4]- rx_in[1:4]+ 1 0 por power management lvttl lvttl signal detect lvttl cml pre- emphasis cml fixed equalizer cml cml fixed equalizer pre- emphasis tx_in[1:4]- tx_in[1:4]+ tx_enable loopback tx_pe[0:1] rx_out[1:4]- rx_out[1:4]+ rx_enable rx_sd[1:4] rx_pe 40k ? 40k ? 40k ? tx_sd[1:4] signal detect limiter limiter v cc 1 v cc 1 v cc 3 v cc 1 v cc 2 v cc 2 v cc 4 lvttl lvttl 40k ? 40k ? v cc 3 v cc 3 v cc 4 v cc 4 v cc 4 v cc 3 v cc 4 v cc 4 v cc 2 v cc 2 v cc 1 v cc 3 MAX3983 figure 3. functional diagram
detailed description the MAX3983 comprises a pc board receiver and cable driver section (tx), as well as a cable receiver and pc board driver section (rx). equalization and sig- nal detection are provided in each receiver, and pre- emphasis is included in each transmitter. the MAX3983 includes separate enable control for the tx outputs and rx outputs. loopback is provided for diagnostic testing. pc board receiver and cable driver (tx_in and tx_out) data is fed into the MAX3983 from the host through a cml input stage and fixed equalization stage. the fixed equalizer in the pc board receiver corrects for up to 20in of pc board loss on fr4 material. the cable dri- ver includes four-state preemphasis to compensate for up to 20m of 24awg, 100 ? balanced cable. table 1 is provided for easy translation between preemphasis expressions. residual jitter of the MAX3983 is indepen- dent of up to 0.17ui p-p source jitter. cable receiver and pc board driver (rx_in and rx_out) the fixed equalizer on each rx input provides approxi- mately 6db equalization to correct for up to 5m of 28awg, 100 ? balanced cable. the pc board driver includes two-state preemphasis to compensate for up to 20in of fr4 material. signal-detect outputs signal detect (sd) is provided on all eight data inputs. pullup resistors should be connected from the sd out- puts to a supply in the 3.0v to 5.5v range. the signal- detect outputs are not valid until power-up is complete. typical signal-detect response time is 0.35s. in the rx section, the sd output asserts high when the rx_in signal amplitude is greater than 175mv p-p . rx_sd deasserts low when the rx_in signal amplitude drops below 85mv p-p . in the tx section, the sd output asserts high when the tx_in signal amplitude is greater than 800mv p-p . tx_sd deasserts low when the tx_in signal amplitude drops below 200mv p-p . tx and rx enable the tx_enable and rx_enable pins enable tx and rx, respectively. typical enable time is 15ns, and typi- cal disable time is 25ns. the enable inputs may be connected to signal-detect outputs to automatically detect an incoming signal (see the autodetect section). power-on reset to limit inrush current, the MAX3983 includes internal power-on reset circuitry. connect a capacitor 0.1f c por 10f from por to ground. with c por = 1f, power-on delay is 6ms (typ). MAX3983 quad copper-cable signal conditioner ______________________________________________________________________________________ 11 table 1. preemphasis translation ratio 10gbase-cx4 in db 1.41 0.17 0.29 3 2.00 0.33 0.50 6 2.82 0.48 0.65 9 4.00 0.60 0.75 12 v v high pp low pp _ _ vv vv high pp low pp high pp low pp __ __ ? + 1 _ _ ? v v low pp high pp 20 log _ _ v v high pp low pp ? ? ? ? ? ? ? ? ? ? ? ? ? ? v low_pp v high_pp
MAX3983 applications information signal-detect output leakage current considerations if all four rx or tx signal-detect outputs are to be con- nected together to form one signal detect, the leakage current of the output stage needs to be considered. each sd output sinks a maximum of 25a when assert- ed, so when four are connected together, a maximum of 100a is possible. the value of the pullup resistor con- nected to pullup voltage v pullup should be selected so the leakage current does not cause the output voltage to fall below the threshold of the next stage. for example, if the signal-detect outputs are connected together and to a stage with a logic-high threshold of 1.5v, the pullup resistor needs to be chosen so v pullup - i leakage x r pullup > 1.5v. in this case, if v pullup = 3.0v, r pullup should be less than 15k ? . autodetect the MAX3983 can automatically detect an incoming sig- nal and enable the appropriate outputs. autodetect of the rx side is done by connecting rx_sd[1:4] together with a pullup resistor (value 4.7k ? to 10k ? to v cc ) to rx_enable. for the tx side, this is done by connecting tx_sd[1:4] together with a pullup resistor (value 4.7k ? to 10k ? to v cc ) to tx_enable (figure 4). if signal is detected on all channels, sd is high and forces the cor- responding enable high. leaving the inputs to the MAX3983 open (i.e., floating) is not recommended, as noise amplification can occur and create undesirable output signals. autodetect is recommended to eliminate noise amplification or possible oscillation. when using autodetect, the link length is determined by the received signal strength. it is possible to reach longer distances if the autodetect configuration is not used. using loopback with autodetect if the MAX3983 is configured for autodetection, rx_enable is controlled by the rx_sd[1:4] outputs. since loopback requires rx_enable to be high, a sim- ple or gate can be used to enable the rx outputs when either rx_sd[1:4] is high or when loopback is high (figure 5). infiniband and 10gbase-cx4 transition time specification infiniband specifies a minimum transition time (20% to 80%) of 100ps and cx4 specifies a minimum of 60ps. both are specified at the connector interface to the cable. the output transition times of the MAX3983 are 45ps (typ) and therefore require some care to increase this time. approximately 3in of fr4 with 4-mil-wide lines is sufficient to lengthen the transition time to 60ps. for 100ps transition times, additional length can be used or an additional 1.5pf capacitor can be placed across the outputs of the MAX3983. do not use high-speed dielec- tric material for the circuit board if the application requires the use of the infiniband or cx4 type connector system. with such materials, the fast edges of the quad copper-cable signal conditioner 12 ______________________________________________________________________________________ MAX3983 rx or tx_sd1 rx or tx_sd2 rx or tx_sd3 rx or tx_sd4 rx or tx_enable 3.0v v pullup 5.5v 4.7k ? r 10k ? figure 4. autodetection using corresponding signal-detect outputs and enable input MAX3983 rx_sd1 rx_sd2 rx_sd3 rx_sd4 rx_enable loopback 3.0v v pullup 5.5v 4.7k ? r 10k ? to host figure 5. loopback in autodetect mode
MAX3983 will produce excessive crosstalk in infiniband and cx4 cable assemblies. crosstalk for infiniband and 10gbase-cx4 applications, it is imperative to know the near-end crosstalk characteristics of the cable assemblies. 10gbase-cx4 has defined the upper limit over frequency for near-end crosstalk (next) with single and multiple aggressors. infiniband has only specified a percentage as measured in the time domain relative to the transmitter output. regardless of the spec- ification method, next is a critical component of the link performance. when using larger amounts of preempha- sis, the received eye height is small and vulnerable to next. for those situations requiring a large transmit pre- emphasis, the next should be less than -30db at fre- quencies from 1ghz to 3ghz. it should be noted that cables that meet the 10gbase-cx4 next and mdnext should provide adequate isolation. layout considerations circuit board layout and design can significantly affect the performance of the MAX3983. use good high-fre- quency design techniques, including minimizing ground inductance and using controlled-impedance transmission lines on the data signals. power-supply decoupling should also be placed as close to the v cc pins as possible. there should be sufficient supply fil- tering. always connect all v cc s to a power plane. take care to isolate the input from the output signals to reduce feedthrough. the performance of the equalizer is optimized for lossy environments. for best results, use board material with a dielectric tangential loss of approximately 0.02 and 4-mil-wide transmission lines. high-speed materials with tangential loss of less than 0.01 can be used, but require special care to reduce near-end crosstalk in cable assemblies. exposed-pad package the exposed-pad, 68-pin qfn package incorporates features that provide a very low thermal resistance path for heat removal from the ic. the pad is electrical ground on the MAX3983 and must be soldered to the circuit board for proper thermal and electrical perfor- mance. for more information on exposed-pad pack- ages, refer to maxim application note hfan-08.1: thermal considerations of qfn and other exposed- paddle packages . interface schematics MAX3983 quad copper-cable signal conditioner ______________________________________________________________________________________ 13 rx_in[1:4]+ tx_in[1:4]+ gnd 50 ? 50 ? rx_in[1:4]- tx_in[1:4]- 5pf v cc x - 1.5v v cc x figure 6. rx_in and tx_in equivalent input structure rx_out[1:4]+ tx_out[1:4]+ gnd 50 ? 50 ? rx_out[1:4]- tx_out[1:4]- v cc x figure 7. rx_out and tx_out equivalent output structure
MAX3983 quad copper-cable signal conditioner 14 ______________________________________________________________________________________ gnd lvttl in 40k ? pin name rx_enable, loopback, rx_pe tx_enable, txpe[0:1] v cc xv cc y v cc 3v cc 4 v cc 1v cc 2 v cc y v cc x figure 8. lvttl equivalent input structure gnd rx_sd[1:4] tx_sd[1:4] figure 9. signal-detect equivalent output structure
MAX3983 quad copper-cable signal conditioner ______________________________________________________________________________________ 15 tx_in3- tx_in3+ gnd tx_in4- tx_in4+ tx_sd3 tx_sd4 tx_enable n.c. tx_out1+ tx_out1- gnd rx_in4+ rx_in4- v cc 3 v cc 3 rx_sd3 rx_sd4 loopback rx_pe 68 qfn* top view tx_pe0 tx_pe1 rx_sd2 rx_sd1 rx_out4- rx_out4+ por rx_enable tx_sd2 v cc 1 v cc 1 tx_in1- tx_in1+ gnd tx_in2- tx_in2+ gnd tx_sd1 v cc 2 v cc 2 v cc 2 v cc 2 v cc 2 tx_out2+ tx_out2- tx_out3+ tx_out3- tx_out4+ tx_out4- gnd rx_in3+ rx_in3- gnd rx_in2+ rx_in2- rx_in1+ rx_in1- rx_out3- rx_out3+ rx_out2- rx_out2+ v cc 4 v cc 4 v cc 4 v cc 4 v cc 4 rx_out1- rx_out1+ *the exposed pad of the qfn package must be soldered to ground for proper thermal and electrical operation of the MAX3983. 41 42 39 40 37 38 35 36 18 19 20 21 22 23 24 25 68 67 66 65 64 63 62 61 11 10 13 12 15 14 17 16 2 1 4 3 6 5 8 7 9 26 27 28 29 30 31 32 33 34 49 50 47 48 45 46 43 44 51 60 59 58 57 56 55 54 53 52 MAX3983 pin configuration chip information transistor count: 7493 process: sige bipolar
MAX3983 quad copper-cable signal conditioner 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. 16 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) 68l qfn.eps c 1 2 21-0122 package outline, 68l qfn, 10x10x0.9 mm c 1 2 21-0122 package outline, 68l qfn, 10x10x0.9 mm

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