1 cml semiconductor products cordless telephone scrambler FX128 d/128/1 october 1997 provisional information features full-duplex audio processing excellent audio quality on-chip filters low power operation (3.0v) carrier rejection >55db ecpa* qualified voice protection uses if (10.24mhz) clock battery powered portability requires no extra crystal cordless telephones and wireless pbx applications 1.1 brief description the FX128 is a full-duplex frequency inversion scrambler designed to provide secure conversations for 46/49 mhz cordless telephone users. the rx and tx audio paths consist of the following: 1 . a switched-capacitor balanced modulator with high baseband and carrier rejection. 2 . a 3.3khz inversion carrier (injection tone). 3 . a 3100hz lowpass filter. 4 . input op-amps with externally adjustable gain. the FX128 uses mixed signal cmos switched-capacitor filter technology and operates from a single supply in the range of 3.0 to 5.5 volts. the inversion carrier's frequency and filter switching clock are generated on-chip using an external 10.24mhz or 3.58/3.6864 mhz crystal or clock input (selectable). this device is available in 16-pin soic (FX128d4) and 16-pin plastic dil (FX128p3) packages. *electronics communications privacy act (title 18, us code 2510 etc.).
2 cordless telephone scrambler FX128 contents section page 1.1 brief descriptio n ....................................................................................... . 1 1.2 block diagra m .......................................................................................... . 3 1.3 signal lis t ................................................................................................ . 4 1.4 external component s ............................................................................... . 5 1.5 applicatio n ............................................................................................. . 6 1.6 application note s ................................................................................... . 6 1.7 performance specificatio n ...................................................................... . 7 1.7.1 electrical performanc e ............................................................ . 7 1.7.2 packagin g ............................................................................... . 10
3 cordless telephone scrambler FX128 1.2 block diagram - + - + clocks and logic r x gai n amp out rxin v bias v bias v bias v dd v dd v ss x t al/clock clr 10.24/3.5 8 mhz clock s e lect x t aln txin t x gai n am p out rx c h annel tx c h annel 212khz 3.3khz rxout txout 0v 2 figure 1 block diagram
4 cordless telephone scrambler FX128 1.3 signal list package d4/p3 signal description pin no. name type 1 xtaln o/p this is the output of the clock oscillator inverter. 2 xtal/clock i/p 10.24mhz or 3.58/3.6864 mhz or an externally derived clock is injected at this pin. see figure 2. 3 - n/c no connection should be made to this pin. 4 txout o/p this is the analogue output of the transmit channel. it is internally biased at v dd /2. 5 tx gain amp out o/p this is the output pin of the transmit gain adjusting op- amp. see figure 3 for gain setting components. 6 txin i/p this is the analogue signal input to the transmit channel. this input goes to a gain adjusting op-amp whose gain is set by external components. see figure 3. 7 - n/c no connection should be made to this pin. 8 vss p ower negative supply (gnd) 9 vbias o/p this is an internally generated bias voltage output (v dd /2) 10 - n/c no connection should be made to this pin. 11 rxin i/p this is the analogue signal input to the receive channel. this input goes to a gain adjusting op-amp whose gain is set by external components. see figure 3. 12 rx gain amp out o/p this is the output pin of the receive gain adjusting op- amp. see figure 3 for gain setting components. 13 rxout o/p this is the analogue output of the receive channel. it is internally biased at v dd /2. 14 clr i/p a logic 1 on this input selects the invert mode. a logic 0 selects the clear (not inverted) mode. 15 clock select i/p selects either 10.24 or 3.58/3.6864 mhz clock frequency. a logic 1 selects 10.24mhz and a logic 0 selects 3.58/3.6864 mhz. this input is internally pulled high. 16 vdd p ower positive supply of 3.0 to 5.5v. notes: i/p = input o/p = output n/c = no connection
5 cordless telephone scrambler FX128 1.4 external components component value value x1 10.24mhz 3.58/3.6864 mhz r1 1.0m w 1.0m w c1 0.47f 0.47f c2 22.0pf 33.0pf c3 22.0pf 47.0pf tolerance: r = 10% c = 20% note : xtal circuitry shown is in accordance with cmls xtal application note. figure 2 recommended external components
6 cordless telephone scrambler FX128 1.5 application 12 120pf 100k 100k 100k 100k 100k 100k rxin rxout 11 13 .1uf .1uf 150pf 150pf 150pf 150pf 5 120pf 100 k 100k txin txout 6 4 .1uf .1uf r f amp rf amp af amp a f am p a f amp hybrid transformer telephone line de-emp pre- emp code detect code encode modul a t or fm detec t or if amp p m m b a s e 12 120pf 100k 100k rxin rxout 11 13 .1uf .1uf 5 120pf 100 k 100k txin txout 6 4 .1uf .1uf r f amp rf amp af amp mic. a f amp spkr de-emp pre- emp code detect code encod e modul a t or key p ad fm detec t or if amp dtmf generation p po r t able FX128 FX128 note : component s shown s e t a g a in o f 0db figure 3 block diagram of a typical application of the FX128 (cordless phone) 1.6 application notes formulae for calculating the carrier frequency, upper cutoff frequency and lower cutoff frequency with clock select pin high are as follows: carrier frequency = (3.2995khz / 10.24mhz) * xtal frequency upper cutoff frequency = (2.800khz / 10.24mhz) * xtal frequency lower cutoff frequency = (400hz / 10.24mhz) * xtal frequency formulae for calculating the carrier frequency, upper cutoff frequency and lower cutoff frequency with clock select pin low are as follows: carrier frequency = (3.2995khz / 3.415mhz) * xtal frequency upper cutoff frequency = (2.800khz / 3.415mhz) * xtal frequency lower cutoff frequency = (400hz / 3.415mhz) * xtal frequency
7 cordless telephone scrambler FX128 1.7 performance specification 1.7.1 electrical performance absolute maximum ratings exceeding these maximum ratings can result in damage to the device. general min max units supply (v dd - v ss ) - 0.3 7.0 v voltage on any pin to v ss -0.3 (v dd + 0.3) v current in or out of v dd and v ss pins -30 +30 ma current in or out of any other pin -20 +20 ma d4 and p3 packages total device dissipation at tamb = 25c 800 mw . . . derating 10 mw/c storage temperature -55 +125 c operating temperature -40 +85 c operating limits correct operation of the device outside these limits is not implied. min. max. units supply (v dd - v ss ) 3.0 5.5 v operating temperature -40 +85 c clock frequency 10.24 mhz
8 cordless telephone scrambler FX128 operating characteristics for the following conditions unless otherwise specified: v dd = 3.3v at tamb = 25c clock frequency = 10.24mhz audio level 0db ref. at 1khz = (v dd - 1) x 150vrms e.g. v dd = 3.3v 0db = 345mvrms notes min. typ. max. units static values supply current - 2.0 3.0 ma input impedance digital 2 100 - - k w amplifiers 2 1.0 10.0 - m w output impedance (rxout, txout) - 1.0 - k w input logic 1 voltage 1 70% - - v dd input logic 0 voltage 1 - - 30% v dd dynamic values general analog signal input levels -16.0 - 3 db analog output noise 4 - 2.5 5.0 mvrms clear mode passband -3db cutoff frequencies low - - 300 hz high 3000 - - hz passband ripple (300-3000hz) rx channel 0 - 3.6 db tx channel 0 - 2.9 db passband ripple (500-2750hz ) rx channel 0 - 2.2 db tx channel 0 - 2.0 db filter attenuation at 3.3khz rx and tx channel - 30 - db filter attenuation at 3.6khz rx and tx channel - 45 - db passband gain (@ 1khz ref.) rx and tx channel -1.5 - 0.5 db switched-capacitor filter sampling - 211.066 - khz carrier frequency - 3298 - h z
9 cordless telephone scrambler FX128 notes min. typ. max. units invert mode combined tx and rx response passband -3db cutoff frequencies low - - 400 hz high 2800 - - hz passband gain -3 - 0.5 db distortion (@ 1khz) 3 - 1.75 2.75 % passband gain (@ 1khz ref.) 5 -2.5 -1.5 0 db low frequency roll-off (<200hz) 12 - - db/oct. invert mode single channel response unwanted modulation products 3 rx and tx channel - -40 - db carrier breakthrough 3 rx and tx channel - -55 - db baseband breakthrough 3 rx and tx channel - -40 - db operating characteristics notes: 1. batch sampled only. 2. by characterisation only. 3. measured with input level 0db. 4. short circuit rx or tx input, measure noise at corresponding analogue output, in 30khz bandwidth. 5. op amp gain 0db. 6. clear mode only.
1 0 1.7.2 package outlines the FX128 is available in the package styles outlined below. mechanical package diagrams and specifications are detailed in section 10 of this document. pin 1 identification marking is shown on the relevant diagram and pins on all package styles number anti-clockwise when viewed from the top. handling precautions the FX128 is a cmos lsi circuit which includes input protection. however precautions should be taken to prevent static discharges which may cause damage. cml does not assume any responsibility for the use of any circuitry described. no circuit patent licences are implied and cml reserves the right at any time without notice to change the said circuitry. o r dering in f ormation FX128d4 16-pin plastic s.o.i.c. (dw) FX128p3 16-pin plastic dil (p) FX128d 4 16-pin plastic s.o.i.c. (dw) FX128p3 16-pin plastic dil (p) not t o scale max. body length 20.57mm max. body width 6.60mm not t o scale max. body length 10.49mm max. body width 7.59mm
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