rds (radio data system) demodulator ic S1A0905X01 1 introduction recovers the rds data which is transmitted by fm radio broadcasting. (european broadcasting union) specifications. the ic includes ? two stage antialiasing filter ? 57khz switched capacitor bandpass filter ? comparator ? 57khz carr ier recovery circuit ? bit rate clock recovery circuit ? bpsk decoder ? differential decoding circuit ? rds signal quality output ordering information device package operating temperature S1A0905X01 16-sop-225 -20 ? +85 c features low current two stage anti- aliasing filter 8'th 57khz switched capacitor bandpass filter dsb demodulation(carrier recovery) clock recovery circuit biphase decoder & differential decoder quality indication output for demodulated data #1 sec S1A0905X01 16 sop (top view) #8 #16 #9
S1A0905X01 rds (radio d ata system) demodulator ic 2 block diagram vref vdda qual datao clko rstb tin vss scbpf8 smoothing filter & comparator mux vssa sgnd comp test vdd xosci xosco scbpf2d scbpf2c scbpf2b scbpf2a 1 16 2 3 4 5 6 7 8 9 10 11 12 13 14 15 xosc & divider dclk generator qual gen differential generator bpsk noise rejector bpsk generator data generator bgr/bias lpf1
rds (radio data system) demodulator ic S1A0905X01 3 pin description qual datao vref mux vdda vssa sgnd comp sec S1A0905X01 test tin vss vdd xosci xosco rstb clko 16 sop (top view) 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8
S1A0905X01 rds (radio d ata system) demodulator ic 4 pin description pin no. symbol in/out function 1 qual o output for signal quality indication. (high = good ,low = bad data) 2 datao o rds data output (1187.5bps) 3 vref o reference voltage output (1/2*vdda) 4 mux i rds signal input (dsb-sc) 5 vdda p analog power supply (5.0v) 6 vssa p 7 sgnd p signal ground 8 comp o positive comparator input 9 test i control pin for test mode.(normal = gnd) 10 tin i input for test mode.(normal = gnd) 11 vss p digital power supply (5.0v) 12 vdd p 13 xosci i crystal oscillator input 14 xosco o crystal oscillator output 15 rstb i input for system reset 16 clko o rds clock output (1.1875khz)
rds (radio data system) demodulator ic S1A0905X01 5 electrical characteristics recommended operating conditions ( ta = 25 c) parameter symbol min. typ. max. unit conditions analog power supply vdda 4.5 - 5.5 v digital power supply vdd 4.5 - 5.5 v operating temperature t op -20 85 c storage temperature t stg -40 150 c electrical characteristics(vdda,vdd = 5.0v,tamp = 25 c, unless otherwise specified) parameter symbol min. typ. max. unit conditions operating current i sum - 4.0 7.0 ma i vdda + i vdd reference voltage vref 2.3 2.5 2.7 v mpx input (signal before the capacitor pin 4) rds amplitude v rds - - 1.0 mvrms d f = 2khz rds maximum input capability v max 0.2 - - vpp input impedance ri 40 - - k w f = 0 to 100khz filter block center frequency fc 56.5 57.0 57.5 khz gain a v 23 26 29 db fc = 57khz att1 31 - - db f = 7khz att2 attenuation att3 40 - - db f < 45khz att4 60 - - db f < 20khz att5 40 - - db f > 70khz signal to noise ratio sn 30 40 - db 57khz vin=3mvrms demodulator block high level output v oh 4.0 - - v low level output v ol - - 0.4 v clock rate c rate - 1187.5 - hz oscillator block oscillation frequency f osc - 4.332 - mhz clock input high level x osci 4.0 - - v clock input low level x osco - - 1.0 v output amplitude x osc - 4.5 - vpp load capacitance cl - 47 - pf
S1A0905X01 rds (radio d ata system) demodulator ic 6 test & application circuit 4.332mhz cko bpfo vcc gnd 473 100uf 220uf 1k 1k 100 47pf 47pf qual do vref 103 22uf mux 104 S1A0905X01 qual datao vref mux vdda vssa sgnd comp test tin vss vdd xosci xosco rstb clko 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 1k 473 100uf 100
rds (radio data system) demodulator ic S1A0905X01 7 output data & clock timing clko datao t1 t2 t3 t 1 = 421 m s t 2 = t 3 = 842 m s the clock(clko) frequency is 1187.5khz. the data (datao) is in synchronous with the rising edge of the clock. to read the valid data, you must use the rising edge of the clock as the reference. the data is valid for 416.7ms. after the reference clock rising edge. qual indicates the quality of the demodulated data. high : good rds data low : poor rds data
S1A0905X01 rds (radio d ata system) demodulator ic 8 band-pass filter characteristics -70 10 30 40 50 60 70 80 90 100 20 -60 -50 -40 -30 -20 -10 0 10 20 30 frequency (khz)
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