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preliminary information describes products that are not in full production at the time of printing. specifications are based on design goals and limited characterization. they may change without notice. contact fairchild semiconductor for current information. www.fairchildsemi.com features rf input frequency range 30 to 250mhz on chip vco with lo frequency range 30 to 250mhz if ampli?r with agc setting high dynamic range -9dbm iip3 on chip video ampli?r built in esd protection supply voltage range 5 to 10 v space saving 20-lead tssop package applications digital set-top receivers cable modems internet surfboards network interface modules multimedia pcs description the rc2798 is an integrated solution for the down- conversion of qam if signals in the front-end design of cable modem and set-top receivers. it is intended for use in 64qam and 256qam if downconversion applications. the rc2798 integrates if ampli?r with agc , mixer, vco, and a video ampli?r on a single chip. it accepts the qam if signals via saw ?ter and downconverts it to 5mhz baseband signal. the baseband signal can be digitized using fairchild semiconductors 8 bit a/d (tmc1175 series) or 10bit a/d (tmc1185 series) and decoded further with a qam demodulator. the if, oscillator and mixer section work at 5v. the video ampli?r works at 5v to 10v. the rc2798 is available in a 20 lead tssop package. block diagram 1 agc_in1 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp videoamp lo agc + mix rc2798 out1 out2 rc2798 integrated qam if downconverter rev 1.0.0
rc2798 product specification 2 absolute maximum ratings (t a = 25 c unless otherwise speci?d) notes: 1. mounted on 50 x 50 x 1.6mm double epoxy glasss board. recommended operating range notes: 1. @ vcc_mix = vccvamp = 4.5 to 5.5v 2. @ vcc_mix = 4.5 to 5.5v, vccvamp = 4.5 to 10.0v parameter test conditions min. typ. max. unit video ampli?r 5v operation vcc_mix supply voltage 1 (for agc amplifier, oscillator, and mixer) agc amplifier, oscillator, and mixer block 6v vccvamp supply voltage 2 ( for video amplifier) video amplifier block 6 v p d power dissipation t a = 85 c 1 430 mw t a operation temperature range -40 +85 c tstg storage temperature range -55 +150 c video ampli?r 9v operation vcc_mix supply voltage 1 (for agc amplifier, oscillator, and mixer) agc amplifier, oscillator, and mixer block 6v vccvamp supply voltage 2 ( for video amplifier) video amplifier block 11 v p d power dissipation t a = 75 c 1 500 mw t a operation temperature range -40 +75 c tstg storage temperature range -55 +150 c parameter min. typ. max. unit vcc_mix supply voltage 1 (for agc amplifier, oscillator, and mixer) 4.5 5.0 5.5 v vccvamp supply voltage 2 ( for video amplifier) 4.5 5.0 10.0 v ta1 operation temperature range 1 1 -40 +25 +85 c ta2 operation temperature range 2 2 -40 +25 +75 c
product specification rc2798 3 electrical characteristics (t a = 25 c ) standard characteristics (v cc = 5v, t a = 25 c) parameter test conditions min. typ. max. unit agc amplifier, oscillator, and mixer blocks (vcc = 5v) icc1 supply current 1 no input signal 17.0 23.0 31.0 ma f rf rf input frequency range 30 250 mhz f osc osc frequency range 30 250 mhz f if if output frequency range dc 150 mhz cg max maximum conversion gain v agc = 4.0v 25 db cg min minimum conversion gain v agc = 1.0v -7 db gcr agc dynamic range v agc = 1.0 to 4.0v 24 32 40 db nf noise figure ssb, v agc = 4.0v at maximum gain 9db v agc h agc voltage high level at maximum gain 4.0 v v agc l agc voltage low level at minimum gain 1.0 v video amplifier block (vcc = 5v) icc2 supply current 2 no input signal 7.0 12.5 17.0 ma v out output voltage rl = 1k w , differential 3.0 vp-p g1 differential gain 1 g1a-g1b pins: short, v out = 3vp-p 150 200 250 v/v g2 differential gain 2 g1a-g1b pins: open, v out = 3vp-p 22.0 26.0 30.0 v/v video amplifier block (vcc = 9v) icc2 supply current 2 no input signal 18.0 24.0 32.0 ma v out output voltage rl = 1k w , differential 3.0 vp-p g1 differential gain 1 g1a-g1b pins: short, rl = 2k w 300 385 470 v/v g2 differential gain 2 g1a-g1b pins: open, rl = 2k w 25.0 28.5 32.0 v/v video amplifier block (vcc = 5v or 9v) bw g1 bandwidth 1 g1 50 mhz bw g2 bandwidth 2 g2 50 mhz rin1 input resistance 1 g1 3.5 k w rin2 input resistance 2 g2 7.5 k w cin input capacitance 1.6 pf parameter test conditions min. typ. max. unit agc amplifier block (vcc = 5v) agc iip3 agc input intercept point at minimum gain (agc amplifier + mixer) -9 dbm video amplifier block (vcc = 5v or 9v) cmrr common mode rejection ratio 80 db psrr power supply rejection ratio 70 db t r rise time 2.6 ns t pd propagation delay time 4.4 ns
rc2798 product specification 4 typical characteristics figure 1. agc control characteristics figure 2. supply current vs. supply voltage -10 -5 0 5 10 15 20 25 30 0 5.00 e-01 1 1.5 2 2.5 3 3.5 4 4.5 5 agc control ?volts conversion gain ?db series1 conv. gain -5.00e-03 0.00e+00 5.00e-03 1.00e-02 1.50e-02 2.00e-02 2.50e-02 3.00e-02 3.50e-02 4.00e-02 4.50e-02 0 4.00 e-01 8.00 e-01 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 6 supply voltage ?volts supply current ?a total agc amp + mixer + lo video amp
product specification rc2798 5 figure 3. measurement circuit 1?gc + mix block 1 agc_in1 10nf 10nf 10nf 10nf 10nf 1k 1k 10nf 10nf 0.22 f fb 10 f10 f 0.1 f 0.1 f + + 10k 51 rf input vagc (1.0?.0v) vcc_mix(+5v) oscillator o/p ext. lo i/p 10k 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 51 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix out mix_out1 g1a g1b vampin1 vampin2 vccamp videoamp lo agc + mix rc2798 out1 out2
rc2798 product specification 6 figure 4. measurement circuit 2?ideo amplifier block 1 agc_in1 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin1 vampin2 vampin2 vccamp vccvamp (+5 or +9v) videoamp lo agc + mix rc2798 out1 out1 out2 out2 10 f10 f 10nf 10nf 0.1 f fb 0.1 f 0.01 f 0.01 f + +
product specification rc2798 7 applications discussion figure 5. application circuit f1 x6964 if input in+ in- 1 1 1 2 3 4 5 6 7 8 9 10 agc_in1 agc_in2 vagc vcc mix osc_out gnd b2 c1 c2 b1 gnd rc2798 mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp out1 out2 20 29 18 17 16 15 14 13 12 11 2 r1 51 2 j1 c1 10nf c11 0.1 f c13 56pf c14 c17 r7 1k1% r8 fb2 fb +9 p2 j4 1k1% r10 1.0k r11 1.0k 0.01 f c19 r9 51 0.01 f c18 0.01 f 56pf c12 vampin2_tp +9v in bb_out out2_tp 0.1 f c15 82pf c16 82pf c20 0.1 f 0.1 f c21 c22 c23 r12 49.9 r13 49.9 + + 10 f 10 f c26 c24 0.01 f c25 0.01 f 15pf c2 10nf c3 r3 10k c4 0.1 f d1 mmbv809 r16 20k r15 20k c30 1000pf c29 c9 c10 ext. lo i/p r4 51 j2 1 2 100pf l3 1.2 h 1000pf 1000pf d2 mmbv809 +5 fb1 fb p1 +5v in gain control input (1.0 - 4.0v) osc_out in_gain vcoc tp_vcoc oscillator output c5 10 f + + c6 10 f c33 10pf c31 15pf c32 15pf c28 0.1 f c7 0.1 f c8 0.01 f r2 10k r18 20k r17 20k 0.22 f gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd j3 1 1 2 2 l1 l2 5.6 h 5.6 h gnd r5 200 1% r6 200 1% gnd gnd gnd gnd gnd gnd notes: 1. for self oscillation, do not load c9, and c10. 2. fro external injection (vco), do not load c28, c29, c30, c31, c32, c33, l3, d1, d2, r15, r16, r17, and r18. 3. for down convesion with video amplifier, do not load c19. 4. for using video amplifier only, do not load c17, c18, c16, c26, and change c15 to 0.1 f. gnd gnd gnd gnd gnd 5 3 4 out+ out- gnd sawfilter
rc2798 product specification 8 crystal oscillator implementation figure 6. fundamental mode?eries resonant xtl figure 7. overtone mode?eries resonant xtl 1 agc_in1 220pf fb 10 f10 f .1 f .1 f + + +5v oscillator o/p xtl 38.886 mhz fundamental mode series resonant 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp rc2798 out1 out2 1 agc_in1 220pf fb 10 f10 f 10nf .1 f .1 f + + +5v oscillator o/p xtl 38.886 mhz co 93pf lo 180nh 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp rc2798 out1 out2
product specification rc2798 9 overtone mode?eries resonant xtl if it is desired to operate a xtl at non-fundamental or overtone frequency, an ac coupled parallel resonant network should be connected to feedback input pin, b1. the typical impedance looking into b1 with b2 ac grounded is approxi- mately rin =1k w @ 38mhz. it is recommended to design the value of qo at approximately 15 to 25. the lo and co values can be calculated from the following equations: qo = w o co rin w o = 2 p fo = (1/loco) 1/2 the xtl is a series resonant type and it is operated at third overtone frequency. figure 8. fundamental or overtone mode?arallel resonant xtl 1 agc_in1 220pf fb 10 f10 f .1 f .1 f + + +5v oscillator o/p xtl 38.886 mhz parallel resonant cc 15pf for fundamental 2pf for overtone 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp rc2798 out1 out2 fundamental or overtone mode?parallel resonant xtl figure 8 shows the implemenation of parallel resonant xtl at fundamental or overtone frequency. the xtl is a parallel resonant type and can be operated at either fundamental or third overtone frequency depending upon the feedback capacitor, cc. when used with cal crystal labs xtl, p/n#ccl-6-38.8860g153, for cc = 15pf it operates at fundamental mode and for cc = 2pf, it operates at third overtone mode (38.886mhz). for symmetrical reasons, the following design is recom- mended for better duty cycle (50 to 50%) output from vco (see figure 9).
rc2798 product specification 10 figure 9. fundamental or overtone mode with improved duty cycle?arallel resonant xtl 1 agc_in1 cc cc fb 10 f10 f .1 f .1 f + + +5v oscillator o/p xtl 38.886 mhz parallel resonant 15pf for fundamental 2pf for overtone cc: 2 agc_in2 3 vagc 4 vcc mix 5 osc_out 6 gnd 7 b2 8 c1 9 c2 10 20 19 18 17 16 15 14 13 12 11 b1 gnd mix_out2 mix_out1 g1a g1b vampin1 vampin2 vccamp rc2798 out1 out2
product specification rc2798 11 package dimensions 20-pin tssop package a .047 1.20 symbol inches min. max. min. max. millimeters notes a1 .002 .006 0.05 0.15 a2 .031 .041 0.80 1.05 .012 0.30 b .007 0.19 c .004 .008 0.09 0.20 e .240 .264 6.10 6.70 e1 .168 .176 4.30 4.50 .018 .029 0.45 0.75 .026 bsc 0.65 bsc e l 0 ? 10 ? 0 ? 10 ? 3 6 2, 4 5 5 n20 20 a ccc .004 0.10 d .250 .257 6.40 6.60 notes: 1. 2. 3. 4. 5. 6. dimensioning and tolerancing per ansi y14.5m-1982. "d" and "e1" do not include mold flash. mold flash or protrusions shall not exceed .010 inch (0.25mm). "l" is the length of terminal for soldering to a substrate. terminal numbers are shown for reference only. "b" & "c" dimensions include solder finish thickness. symbol "n" is the maximum number of terminals. e e1 a a2 d e b a1 ?c ccc c lead coplanarity seating plane a l c
rc2798 product specification 5/20/98 0.0m 001 stock#ds30002798 1998 fairchild semiconductor corporation life support policy fairchild? products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor corporation. as used herein: 1 . life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2 . a critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com o r dering in f ormation p r oduct number p a c k age rc2798g 20 pi n tssop
product folder - fairchild p/n rc2798 - integrated qam if downconverter fairchild semiconductor space space space search | parametric | cross reference | inventory space product folders and datasheets application notes space space space find products home >> find products >> space space space space products groups space analog and mixed signal discrete interface logic microcontrollers non-volatile memory optoelectronics markets and applications new products product selection and parametric search cross-reference search technical information buy products technical support my fairchild company rc2798 integrated qam if downconverter related links request samples dotted line how to order products dotted line product change notices (pcns) dotted line support dotted line distributor and field sales representatives dotted line quality and reliability dotted line design tools contents general description | features | applications | product status/pricing/packaging general description the rc2798 is an integrated solution for the down-conversion of qam if signals in the front-end design of cable modem and set-top receivers. it is intended for use in 64qam and 256qam if downconversion applications. the rc2798 integrates if amplifier with agc , mixer, vco, and a video amplifier on a single chip. it accepts the qam if signals via saw filter and downconverts it to 5mhz baseband signal. the baseband signal can be digitized using fairchild semiconductor's 8 bit a/d (tmc1175 series) or 10bit a/d (tmc1185 series) and decoded further with a qam demodulator. the if, oscillator and mixer section work at 5v. the video amplifier works at 5v to 10v. the rc2798 is available in a 20 lead tssop package. back to top features space datasheet download this datasheet pdf e-mail this datasheet [e- mail] this page print version file:///d|/fair/pdf/rc2798.html (1 of 2) [10/7/02 11:12:27 am]
product folder - fairchild p/n rc2798 - integrated qam if downconverter l rf input frequency range 30 to 250mhz l on chip vco with lo frequency range 30 to 250mhz l if amplifier with agc setting l high dynamic range -9dbm iip3 l on chip video amplifier l built in esd protection l supply voltage range 5 to 10 v l space saving 20-lead tssop package back to top applications l digital set-top receivers l cable modems l internet surfboards l network interface modules l multimedia pcs back to top product status/pricing/packaging product product status pricing* inventory check & ordering package marking packing method rc2798g lifetime buy $1.43 purchase $y&z&2&t rc2798g rail RC2798GT lifetime buy $1.43 purchase $y&z&2&t rc2798g tape reel * fairchild 1,000 piece budgetary pricing back to top space space home | find products | technical information | buy products | support | company | contact us | site index | privacy policy ? copyright 2002 fairchild semiconductor space space file:///d|/fair/pdf/rc2798.html (2 of 2) [10/7/02 11:12:27 am]

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