description up to 2.5gbps 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 sy88922 and sy88904 or sy88905 available in a tiny 10-pin (3mm) msop the SY88923 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 2.5gbps. signals as small as 5mvp-p can be amplified to drive devices with pecl inputs. the SY88923 generates a chatter-free loss of signal (los) open collector ttl output. the SY88923 incorporates a programmable 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 condition. using los lvl pin, the sensitivity of the level detection can be adjusted. the los lvl voltage can be set by connecting a resistor divider between v cc and v ref . figure 3 and figure 4 show 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 a pull-up resistor for proper operation, figure 1. features 2.5gbps high-speed limiting post amplifier SY88923 final applications 1.25gbps gigabit ethernet 531mbps and 1062mbps fibre channel 622mbps sonet gigabit interface converter 2.5gbps sdh/sonet pin configuration block diagram 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 figure 1. los output with desired rise time SY88923 los +5.0v 2k limiting amplifer ecl buffer d in d in v ref v cc gnd los lv l enable level detect d out d out en los 1 rev.: c amendment: /1 issue date: july 2000
2 SY88923 micrel pin type function d in data input data input /d in data input inverting data input los lvl input los limit 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 inverting data output d out pecl output data output v cc power supply positive power supply v ref output reference voltage output for los level set (see fig. 3) general the SY88923 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 SY88923 limiting amplifier quantizes the signal and outputs a voltage- limited waveform. the /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 SY88923 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 (8) ?.3 (8) ?.3 (8) ?.3 (8) ?a 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 ?.0 gnd +2.0 v cc ?.0 gnd +2.0 ? cc ?.0 gnd +2.0 v cc ?.0 v v offset differential output offset 100 100 100 100 mv los lvl los lvl level (2) v ref v cc v ref v cc v ref ? cc v ref v cc v v ol los output low level (3) 0.5 0.5 0.5 0.5 v i oh los output leakage (4) 250 250 250 250 ua v oh d out and /d out v cc ?085 v cc ?80 v cc ?025 v cc ?80 v cc ?025 v cc ?55 v cc ?80 v cc ?025 v cc ?80 mv high output v ol d out and /d out v cc ?830 v cc ?555 v cc ?810 v cc ?620 v cc ?810 v cc ?705 v cc ?620 v cc ?810 v cc ?620 mv low output v ref reference supply (7) v cc ?.625 v cc ?.325 v cc ?.625 v cc ?.325 v cc ?.625 v cc ?.475 v cc ?.325 v cc ?.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. 2 23 -1 pattern. 3. i ol = + 2ma. 4. 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 5. v in = 2.7. 6. v in =v cc. 7. i ref must be limited within ?.8ma (source) and 0.4ma (sink). 8. v in = 0.5v . 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 175 175 175 175 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 2 23 -1 pattern 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 3. input is a 200mhz square wave, tr < 300ps, 8mvp-p. 4. input is a 200mhz square wave, tr < 300ps, 1.8vp-p. notes: 1. input referred noise = rms output noise/low frequency gain. 2. input is a 622mhz square wave.
4 SY88923 micrel aaaaaaaaaaaaaaaaaaaaa a a a a a a a a a a a a a a a a a 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 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 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 los lvl (v) level (mv) deassert assert output termination the SY88923 outputs must be terminated with a 50 ? load to v cc 2v (or thevenin equivalent). layout and pcb design since the SY88923 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 power supply. the SY88923 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. design procedure figure 3. loslvl circut note: resistor divider = r2/ (r1 + r2) r1 + r2 5k ? figure 2. differential input configuration d in+ d in v ref 50 ? 50 ? 0.1 f 0.1 f 0.1 f v cc r1 r2 los lv l v ref performance curve figure 4. 2 23 -1 pattern figure 5. 2 23 -1 pattern 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 r2 / (r1 + r2) deassert assert los assert and deassert levels vs resistor divide 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 level (mv)
5 SY88923 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 200 ? v cc gnd 200 ? 68 ? 68 ? v cc en v cc gnd v cc gnd d out d out 200 ? 200 ? 68 ? 68 ? 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 SY88923 0.1f 20k ? 0.1f 130 ? 130 ? 82 ? 82 ? v cc 20k ? sy88922 v ref r set the value of rser depends on the laser diode. v cc v cc product ordering code ordering package operating code type range SY88923kc k10-1 commercial
6 SY88923 micrel 10 lead msop (k10-1) rev. 00
7 SY88923 micrel
8 SY88923 micrel micrel-synergy 3250 scott boulevard santa clara ca 95054 usa tel + 1 (408) 980-9191 fax + 1 (408) 914-7878 web http://www.synergysemi.com 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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