description up to 1.25gbps operation low noise chatter-free los generation open collector ttl los output ttl /en input differential pecl inputs for data single power supply designed for use with sy88902 and sy88904 available in a tiny 10-pin (3mm) msop the SY88903 limiting post amplifier with its high gain and wide bandwidth is ideal for use as a post amplifier in fiber-optic receivers with data rates up to 1.25gbps. signals as small as 5mvp-p can be amplified to drive devices with pecl inputs. the SY88903 generates a chatter-free loss of signal (los) open collector ttl output. the SY88903 incorporates a programmble level detect function to identify when the input signal has been lost. this information can be fed back to the /en input of the device to maintain stability under loss of signal conditions. using los lvl pin the sensitivity of the level detect can be adjusted. the los lvl voltage can be set by connecting a resistor divider between v cc and v ref , figure 3. figure 4 shows the relationship between input level sensitivity and the voltage set on los lvl . figure 5 shows the relationship between input level sensitivity and resistor divider ratio. the los output is a ttl open collector output that requires pull-up resistor for proper operation, figure 1. SY88903 los +5v 2k figure 1. los output with desired rise time features 1.25gbps high-speed limiting post amplifier SY88903 final applications 1.25gbps gigabit ethernet 531mbps and 1062mbps fibre channel 622mbps sonet gigabit interface converter block diagram limiting amplifier d in d in level detect ecl buffer enable d out d out los lvl los gnd v cc en v ref pin configuration 1 /en d in /d in v ref los lv l 10 v cc d out /d out los gnd 9 8 7 6 2 3 4 5 msop k10-1 1 rev.: g amendment: /1 issue date: july 2000
2 SY88903 micrel pin type function d in data input data input /d in data input inverting data input los lvl input loss of signal level set /en ttl input output enable (active low) los ttl output loss of signal indicator (open collector) (active high) gnd ground ground d out pecl output data output /d out pecl output inverting data output v cc power supply positive power supply v ref output reference voltage output for los level set (see fig. 3) general the SY88903 is an integrated limiting amplifier intended for high-frequency fiber-optic applications. the circuit connects to typical transimpedance amplifiers found within a fiber-optics link. the linear signal output from a transimpedance amplifier can contain significant amounts of noise, and may vary in amplitude over time. the SY88903 limiting amplifier quantizes the signal and outputs a voltage- limited waveform. the ttl /en pin allows the user to disable the output signal without removing the input signal. pin names general description symbol rating value unit v cc power supply voltage 0 to +7.0 v d in , /d in input voltage 0 to v cc v d out , /d out output voltage (with 50 ? load) v cc ?.5, v cc +0.3 v t a operating temperature range ?0 to +85 c t store storage temperature range ?5 to +125 c absolute maximum ratings (1) note: 1. permanent device damage may occur if absolute maximum ratings are exceeded. this is a stress rating only and functional oper ation is not implied at conditions other than those detailed in the operational sections of this data sheet. exposure to absolute maximum ratlng co nditions for extended periods may affect device reliability.
3 SY88903 micrel t a = ?0 ct a = 0 ct a = +25 ct a = +85 c symbol parameter min. max. min. max. min. typ. max. min. max. unit i cc power supply current (1) 35 35 21 35 35 ma i il /en input low current ?.3 ?.3 ?.3 ?.3 ma i ih /en input high current ?0 (5) ?0 (5) 20 (5) ?0 (5) a 100 (6) 100 (6) 100 (6) 100 (6) v cmr common mode range gnd +2.0 v cc -1.0 gnd +2.0 v cc -1.0 gnd +2.0 ? cc -1.0 gnd +2.0 v cc -1.0 v v offset differential output offset 100 100 100 100 mv los lvl los lvl level v ref v cc v ref v cc v ref ? cc v ref v cc v v ol los output low 0.5 0.5 0.5 0.5 v level (2) i oh los output leakage (3) 250 250 250 250 ua v oh d out and /d out v cc -1085 v cc -880 v cc -1025 v cc -880 v cc -1025 v cc -955 v cc -880 v cc -1025 v cc -880 mv high output v ol d out and /d out v cc -1830 v cc ?555 v cc -1810 v cc ?620 v cc -1810 v cc ?705 v cc ?620 v cc -1810 v cc ?620 mv low output v ref reference supply (4) v cc -2.625 v cc ?.325 v cc -2.625 v cc ?.325 v cc -2.625 v cc ?.475 v cc ?.325 v cc -2.625 v cc ?.325 v v ih /en input high voltage 2.0 2.0 2.0 2.0 v v il /en input low voltage 0.8 0.8 0.8 0.8 v notes: 1. no output load 2. i ol = + 2ma 3. v oh = 5.5v dc electrical characteristics v cc = +5v 10%, r load = 50 ? to v cc -2v, t a = ?0 c to +85 c 4. i ref must be limited to be within -0.8ma (source) and 0.5ma (sink). 5. v in = 2.7v 6. v in = v cc t a = ?0 ct a = 0 ct a = +25 ct a = +85 c symbol parameter min. max. min. max. min. typ. max. min. max. unit conditions psrr power supply (1) 35 db input referred, rejection ratio 55mhz v id input voltage range 5 1800 5 1800 5 1800 5 1800 mvp-p t r, t f output rise/fall time 350 350 200 350 350 ps v id > 100mvp-p t rin ,t fin v id < 100mvp-p v od differential output 600 mv v id = 15mvp-p voltage swing (2) 200 mvv id = 5mvp-p t offl los release time (3) 0.5 0.5 0.1 0.5 0.5 s minimum input t offh los release time (4) 0.5 0.5 0.1 0.5 0.5 s maximum input t onl los assert time (3) 0.5 0.5 0.2 0.5 0.5 s v sr los sensitivity range 5 50 5 50 5 50 5 50 mvp-p hys los hysteresis 2 8 2 8 2 4.6 8 2 8 db ac electrical characteristics v cc = +5v 10%, r load = 50 ? to v cc - 2v, t a = ?0 c to +85 c notes: 1. input referred noise = rms output noise/low frequency gain. 2. input is 622mhz square wave. 3. input is a 200mhz square wave, tr < 300ps, 8mvp-p. 4. input is a 200mhz square wave, tr < 300ps, 1.8vp-p.
4 SY88903 micrel product ordering code ordering package operating code type range SY88903kc k16-1 commercial output termination the SY88903 outputs must be terminated with a 50 ? load to v cc ?2v (or thevenin equivalent). layout and pcb design since the SY88903 is a high-frequency component, performance can largely be determined by board layout and design. a common problem with high-gain amplifiers is feedback from the large swing outputs to the input via the power supply. d in d in + v ref 0.1f 0.1f 50 ? 50 ? 0.1f figure 2. differential input configuration application information the SY88903 ground pin should be connected to the circuit board ground. use multiple pcb vias close to the part to connect to ground. avoid long, inductive runs which can degrade performance. notes: resistor divider = r2/ (r1 + r2) r1 + r2 5k ? los lvl v ref r1 r2 v cc figure 3. los lvl circut
5 SY88903 micrel performance curve aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 2.53 2.65 2.77 2.90 3.02 3.14 3.27 3.39 3.52 3.64 3.76 3.89 4.01 4.13 4.26 4.38 4.51 4.63 4.75 4.88 5.00 loslvl (v) level (mv) deassert assert figure 4. los assert and deassert levels vs los lvl 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 resistor divider r 2 / ( r 1 + r 2 ) level (mv) deassert assert figure 5. los assert and deassert levels vs resistor divider
6 SY88903 micrel application example for 3-chip set solution d in d in gbic terminal en rx_data rx_data+ tx_data tx_data+ rx_los enable/disable 130 ? v cc gnd 130 ? 82 ? 82 ? v cc en v cc gnd v cc gnd d out d out 130 ? 130 ? 82 ? 82 ? v cc out out d in 24 ? v cc r ext r ser laserdiode photodiode v ref md i bias los out los in d in los lvl i bias set sy88905 20k ? 20k ? 1000pf blm21a102s laser module i bias fb i pin set los v ref SY88903 0.1f 20k ? 0.1f 130 ? 130 ? 82 ? 82 ? v cc 20k ? sy88902 v ref r set the value of rser depends on the laser diode. v cc v cc
7 SY88903 micrel 10 lead msop (k10-1) rev. 00
8 SY88903 micrel micrel-synergy 3250 scott boulevard santa clara ca 95054 usa tel + 1 (408) 980-9191 fax + 1 (408) 914-7878 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 2000 micrel incorporated
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