1 SY88903 micrel, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 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 not recommended for new designs SY88903 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 rev.: i amendment: /0 issue date: june 2007
2 SY88903 micrel, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 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 C2.5, v cc +0.3 v t a operating temperature range C40 to +85 c t store storage temperature range C55 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 condi tions for extended periods may affect device reliability. package/ordering information 10-pin msop (k10-1) ordering information package operating package lead part number type range marking finish SY88903kc k10-1 commercial 903 sn-pb SY88903kctr(1) k10-1 commercial 903 sn-pb SY88903kh k10-1 commercial 903 with pb-free pb-free bar-line indicator nipdau SY88903khtr(1) k10-1 commercial 903 with pb-free pb-free bar-line indicator nipdau note: 1. tape and reel. 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
3 SY88903 micrel, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 t a = C40 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) 35352 135 35ma i il /en input low current C0.3 C0.3 C0.3 C0.3 ma i ih /en input high current 20 (5) 20 (5) 20 (5) 20 (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 v 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 v 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 C1555 v cc -1810 v cc C1620 v cc -1810 v cc C1705 v cc C1620 v cc -1810 v cc C1620 mv low output v ref reference supply (4) v cc -2.625 v cc C2.325 v cc -2.625 v cc C2.325 v cc -2.625 v cc C2.475 v cc C2.325 v cc -2.625 v cc C2.325 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 = C40 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 = C40 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) 3 5 db input referred, rejection ratio 55mhz v id input voltage range 5 1800 5 1800 5 1800 5 1800 mv pp t r, t f output rise/fall time 350 350 200 350 350 ps v id > 100mv pp t rin ,t fin v id < 100mv pp v od differential output 600 mv v id = 15mv pp voltage swing (2) 200mvv id = 5mv pp 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 mv pp 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 = C40 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, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 output termination the SY88903 outputs must be terminated with a 50 ? load to v cc C 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 C 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, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 performance curve 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, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 application example for 3-chip set solution d in d in gbic terminal en rx_dataC rx_data+ tx_dataC 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, inc. m9999-061907 hbwhelp@micrel.com or (408) 955-1690 10 lead msop (k10-1) rev. 00 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 web http://www.micrel.com the information furnished by micrel in this data sheet is believed to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intend ed for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant inj ury to the user. a purchasers use or sale of micrel products for use in life support appliances, devices or systems is at purchasers own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2005 micrel, incorporated.
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