M908-01 datasheet rev 1.2 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 M908-01 vcso b ased g b e c lock g enerator integrated circuit systems, inc. preliminary information g eneral d escription the M908-01 is a pll (phase locked loop) based clock generator that uses an internal vcso (voltage controlled saw oscillator) to produce a very low jitter output clock. it is ideal for gigabit ethernet. an output clock frequency of 156.25 mhz (with the M908-01-156.2500 ) is provided from eight lvpecl clock output pairs. the accuracy of the output frequency is assured by the internal pll that phase-locks the internal vcso to the reference input frequency ( 25 mhz for the M908-01-156.2500 ). the input reference can either be an external crystal, utilizing the internal crystal oscillator, or a stable external clock source such as a packaged crystal oscillator. f eatures 156.25mhz output clock frequency ( M908-01-156.2500 ) eight identical lvpecl output pairs jitter 0.7ps rms (over 12khz-20mhz) ideal for gigabit ethernet clock reference output-to-output skew < 100 ps external xtal or lvcmos reference input integrated saw (surface acoustic wave) delay line single 3.3v power supply small 9 x 9 mm smt (surface mount) package p in a ssignment (9 x 9 mm smt) figure 1: pin assignment s implified b lock d iagram figure 2: simplified block diagram output frequency configuration ( M908-01-156.25 ) ref clock frequency (mhz) pll ratio output frequency (mhz) application 25 25/4 156.25 gigabit ethernet table 1: output frequency c onfiguration (M908-01-156.25) M908-01 (top view) xtal_1 / ref_in gnd nfout5 fout5 nfout4 fout4 nfout3 fout3 vcc nfout2 fout2 nfout1 fout1 gnd nfout0 fout0 vcc gnd xtal_2 fout6 nfout6 fout7 nfout7 vcc dnc dnc dnc nop_in op_out vc nvc nop_out op_in gnd gnd gnd 19 20 21 22 23 24 25 26 27 1 2 3 4 5 6 7 8 9 29 30 31 32 33 34 35 36 28 17 16 15 14 13 12 11 10 18 xtal osc external crystal or reference clock input (25mhz) lvpecl output clock pairs (156.25mhz) divider vsco frequency multiplying pll external loop filter M908-01-156.25 fout2 nfout2 fout4 nfout4 fout3 nfout3 fout6 nfout6 fout5 nfout5 fout7 nfout7 fout0 nfout0 fout1 nfout1 M908-01 vcso based gbe clock generator http://www..net/ datasheet pdf - http://www..net/
M908-01 datasheet rev 1.2 2 of 6 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 integrated circuit systems, inc. M908-01 vcso b ased g b e c lock g enerator preliminary information d etailed b lock d iagram figure 3: detailed block diagram p in d escriptions number name i/o configuration description 1,2,3,10,14,26 gnd ground power supply ground. 4,9 op_in, nop_in input used for external loop filter. see figure 4 . 5,8 nop_out, op_out output 6, 7 nvc, vc input 11,19,33 vcc power power supply connection, connect to + 3.3 v 12,13 fout0, nfout0 output no internal terminator clock output pairs, differential lvpecl output ( 156.25 mhz for the M908-01-156.2500 ) 15,16 fout1, nfout1 17,18 fout2, nfout2 20,21 fout3, nfout3 22,23 fout4, nfout4 24,25 fout5, nfout5 29,30 fout6, nfout6 31,32 fout7, nfout7 27 xtal_1 / ref_in input external crystal connection. also accepts lvcmos/lvttl compatible clock source. 28 xtal_2 input external crystal connection. leave unconnected when driving pin 27 with external clock reference. 34,35,36 dnc do not connect. internal test pins. table 2: pin descriptions M908-01 xtal_2 xtal_1 / ref_in xtal osc r divider r = 4 phase detector vcso saw delay line phase shifter vcso c post c post vc nvc r post nop_out op_out r post r loop r loop c loop c loop r in r in op_in nop_in loop filter amplifier external loop filter components m divider m = 25 phase locked loop (pll) fout2 nfout2 fout4 nfout4 fout3 nfout3 fout6 nfout6 fout5 nfout5 fout7 nfout7 fout0 nfout0 fout1 nfout1 http://www..net/ datasheet pdf - http://www..net/
M908-01 datasheet rev 1.2 3 of 6 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 M908-01 vcso b ased g b e c lock g enerator preliminary information integrated circuit systems, inc. f unctional d escription the M908-01 is a pll (phase locked loop) based clock generator that generates output clocks synchronized to an input reference clock. the M908-01 combines th e flexibility of a vcso (voltage controlled saw oscill ator) with the stability of a crystal oscillator. input reference the 25mhz input reference can either be an external, discrete crystal device or a stable external clock source such as a packaged crystal oscillator: ? if an external crystal is used with the on-chip crystal oscillator circuit (xtal osc), the external crystal should be a parallel-resonant, fundamental mode crystal. apply it to the xtal_1 / ref_in and xtal_2 input pins. external crystal load capacitors are also required. ? if an external lvcmos/lvttl clock source is used, apply it to the xtal_1 / ref_in input pin. in either case, the reference clock is supplied to the phase detector of the pll. the M908-01 includes a reference divider that divides the input reference frequency by a fixed value ?r? and provides the result to the phase detector. the pll the pll (phase locked loop) includes the phase detector, the vcso, a feedback divider (labeled ?m divider?), and a reference divider (?r divider?). the feedback divider divides the vcso output frequency by a fixed value ?m? to match the reference frequency provided to the phase detector by the reference divider. by controlling the frequency and phase of the vcso, the phase detector precisely locks the frequency and phase of the feedback divider output to that of the reference divider output. this creates an output frequency that is a multiple of the reference frequency (which is output from the vcso). the relationship between the vcso output frequency, the m divider, the r divider and the input reference frequency is defined as follows: for the M908-01-156.2500 (see ?ordering information? on pg. 6 ): ? vcso output frequency = 156.25mhz ? input reference frequency = 25mhz ? m=25 ? r= 4 therefore, for the M908-01-156.2500 : 25 156.25mhz = 25mhz 4 the vcso center output frequency of 156.25mhz enables the product of the input crystal frequency to fall within the lock range of the vcso. external loop filter to provide stable pll operation, and thereby a low jitter output clock, the M908-01 requires the use of an external loop filter. this is provided via the provided filter pins (see figure 4 ). due to the differential signal path design, the implementation requires two identical complementary rc filters as shown here. figure 4: external loop filter fvcso fxtal m r ---- - = external loop filter component values pll bandwidth damping factor r loop c loop r post c post 500 hz 2.1 1.5 k ? 4.00 f 50 k ? 3300 pf 1.5 khz 3.3 4.7 k ? 1.00 f 50 k ? 1500 pf 6.4 khz 4.4 20 k ? 0.10 f 20 k ? 470 pf 10.6 khz note 1: recommended for most applications 4.2 33 k ? 0.033 f 20 k ? 470 pf table 3: external loop filter component values --------- - c post c post v c nvc r post nop_out op_out r post r loop r loop c loop c loop op_in nop_in 6 7 5 49 8 http://www..net/ datasheet pdf - http://www..net/
M908-01 datasheet rev 1.2 4 of 6 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 integrated circuit systems, inc. M908-01 vcso b ased g b e c lock g enerator preliminary information a bsolute m aximum r atings 1 symbol parameter rating unit v i inputs - 0.5 to v cc + 0.5 v v o outputs - 0.5 to v cc + 0.5 v cc power supply voltage 4.6 t s storage temperature - 45 to + 100 o c table 4: absolute maximum ratings note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these ratings ard stress s pecifications only. func tional operation of produc t at these conditions or any conditions beyond those listed in recommended conditions of operation , dc characteristics , or ac characteristics is not implied. exposure to absolute maxi mum rating conditions for extended periods may affect product reliability . r ecommended c onditions of o peration symbol parameter min typ max unit v cc positive supply voltage 3.135 3.3 3.465 v t a ambient operating temperature 0 + 70 o c table 5: recommended c onditions of operation http://www..net/ datasheet pdf - http://www..net/
M908-01 datasheet rev 1.2 5 of 6 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 M908-01 vcso b ased g b e c lock g enerator preliminary information integrated circuit systems, inc. e lectrical s pecifications dc characteristics unless stated otherwise, v cc = 3.3 volts + 5%, t a = 0 o c to 70 o c, output frequency=156.25mhz 1 , outputs terminated with 50 ? to v cc - 2v symbol parameter min typ max unit power supply v cc positive supply voltage 3.135 3.3 3.465 v i cc power supply current 350 ma reference clock input v ih input high voltage xtal_1 / ref_in (xtal_2 disconnected) (v cc / 2 ) + 0.5 v cc + 0.3 v v il input low voltage - 0.3 (v cc / 2 ) + 0.5 v i ih input high current 150 a i il input low current - 5.0 a crystal or reference clock input c in input capacitance xtal_1 / ref_in 4 pf differential output v oh output high voltage fout, nfout (0-7) v cc - 1.4 v cc - 1.0 v v ol output low voltage v cc - 2.0 v cc - 1.7 v v p - p peak to peak output voltage 0.6 0.85 v table 6: dc characteristics note 1: for other vcso center frequencies, contact ics ac characteristics unless implied otherwise, v cc = 3.3 volts + 5%, t a = 0 o c to 70 o c, output frequency=156.25mhz 1 , outputs terminated with 50 ? to v cc - 2v symbol parameter min typ max unit test conditions f out output frequency range 75 156.25 175 mhz f in nominal input frequency, xtal_1 / ref_in 25 mhz apr vcso pull-range + 100 + 150 ppm n single side band phase noise @ 156.25 mhz 1 khz offset - 100 dbc/hz 10 khz offset - 110 dbc/hz 100 khz offset - 134 dbc/hz j(t) jitter (rms) 0.7 1.0 ps 12 khz to 20 mhz t dc output duty cycle, high time 45 50 55 % t r output rise time fout, nfout (0-7) 350 450 550 ps 20 % to 80 % t f output fall time fout, nfout (0-7) 350 450 550 ps 20 % to 80 % t s output skew between any pair 100 ps table 7: ac characteristics note 1: for other vcso center frequencies, contact ics http://www..net/ datasheet pdf - http://www..net/
M908-01 datasheet rev 1.2 6 of 6 revision 013003 integrated circuit systems, inc. communications modules www.icst.com tel (508) 852-5400 integrated circuit systems, inc. M908-01 vcso b ased g b e c lock g enerator preliminary information p ackage - m echanical d imensions o rdering i nformation consult factory for frequency availability. while the information presented herein has been checked for both accuracy and reliability, integrated circuit systems (ics) assumes no responsibility for either its use or for the infringement of any patents or other rights of third parties, which wou ld result from its use. no other circuits, patents, or licenses are implied. this product is intended for use in normal commercial applications. any other applications such as those requiring ex tended temperature range, high reliability, or other extraordina ry environmental requirements are not recommended without additional processing by ics. ics reserves the right to change any circuitry or specifications without notice. ics does not authorize or warrant any ics product for use in life support devices o r critical medical instruments. key to dimensions e.g., .016 [0.4] inches [mm] for output frequencies (mhz) order part number 156.25 M908-01-156.2500 table 8: ordering information http://www..net/ datasheet pdf - http://www..net/
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