bu1924 / bu1924f audio ics 1/5 rds / rbds decoder bu1924 / bu1924f the bu1924 and bu1924f are rds / rbds decoders that employ a digital pll and have a built-in anti-aliasing filter and an eight-stage bpf (switched-capacitor filter). linear cmos circuitry is used for low power consumption. ! ! ! ! applications rds / rbds compatible fm receivers for american and european markets, car stereos, high-fidelity stereo systems and components, and fm pagers. ! ! ! ! features 1) low current. 2) two-stage anti-aliasing filter (lpf). 3) 57khz band-pass filter. 4) dsb demodulation (digital pll). 5) quality indication output for demodulated data. ! ! ! ! absolute maximum ratings (ta = 25 c) parameter symbol limits conditions unit power supply voltage v dd ? 0.3~ + 7.0 v maximum input voltage v max. ? 0.3~v dd + 0.3 v maximum output voltage i max. 4.0 ma power dissipation pd 350 ? mw operating temperature topr ? 40~ + 85 c storage temperature tstg ? 55~ + 125 c v dd1 v dd2 all input pins all output pins ? reduced by 3.5mw for each increase in ta of 1 c over 25 c. ? ? ? ! ! ! ! recommended operating conditions (ta = 25 c) parameter v dd1 2.7 5.5 v ? power supply voltage v dd2 2.7 5.5 v ? symbol min. typ. max. unit
bu1924 / bu1924f audio ics 2/5 ! ! ! ! block diagram 560p cmp v ss3 comparator 8th switched capacitor filter anti-aliasing filter 100k ? 120k ? 100k ? 270p mux vref 2.2 f v dd1 ? 1 analog power supply v ss1 ? 1 v dd2 ? 2 digital power supply v ss2 xi xo 4.332mh z 33pf ? 3 33pf ? 3 pll 57kh z rds/ari pll 1187.5hz bi-phase decoder measurement circuit differential decoder t1 t2 rdata qual rclk ? 1 : v dd1 and v dd2 are separated within the ic. ? 2 : have v dd2 (digital power supply) of a sufficiently low impedance. ? 3 : match the capacitor constants with the crystal manufacturer. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 rclk (n.c.) xo xi v dd2 v ss2 t1 t2 qual rdata vref mux v dd1 v ss1 v ss3 cmp reference clock (4) (3) (5) (6) (12) (11) (13) (14) (10) (7) (8) (16) (2) (9) (1)
bu1924 / bu1924f audio ics 3/5 ! ! ! ! pin descriptions pin no. pin name symbol functions input/output type 1 qual demodulator quality type c good data : high, bad data : low refer to output data timing 6v s s1 7 8 2 rdata demodulator data 9t2 test input type b open or connected to ground 10 t1 3 vref reference voltage 4 mux input type e type f 1/2 v d d1 (refer to input/output circuits) composite signal input (refer to input/output circuits) 11 v ss 2 digital power supply 2.7v to 5.5v 12 v dd 2 13 xi crystal oscillator type a connects to 4.332mhz oscillator (refer to input/output circuits) 14 xo 15 (n.c.) ?? type c 16 rclk demodulator clock 1187.5hz clock (refer to the timing diagram) 5v d d1 analog power supply 2.7v to 5.5v cmp comparator input type d c-junction (refer to input/output circuits ) type c ? v s s3 gnd ? ? ? ? ! ! ! ! input / output circuits vref type a type b type d type c type e type f + 10m ?
bu1924 / bu1924f audio ics 4/5 ! ! ! ! electrical characteristics (unless otherwise noted, ta = 25 c, v dd1 = v dd2 = 5.0v, v ss1 =v ss2 = v ss3 = 0.0v) parameter symbol min. typ. max. unit conditions operating current i dd ? 6.5 10.0 ma i dd1 + i dd2 reference voltage vref ? 1/2v dd1 ? v pin 3 input current 1 i in1 ?? 1.0 a mux mux output current 1 i out1 ?? 1.0 a v in = v ss1 v in = v dd1 input current 2 i in2 ?? 1.0 axi xi output current 2 i out2 ?? 1.0 av in = v ss2 v in = v dd2 output high level voltage 1 v oh1 v dd2 v dd2 ? v rclk rdata qual i o =? 1.0ma output low level voltage 1 v ol1 ? 0.2 1.0 v rclk rdata qual i o = 1.0ma rds detector sensitivity srds ? ? 0.5 1.0 mvrms rds input level mrds 1.0 ? 300 mvrms data rate drate ? 1187.5 ? hz clock transient vs. data ct ? 4.3 ? s center frequency fc 56.5 57.0 57.5 khz gain ga 20 23 26 db f = 57.0khz attenuation 1 att1 18 22 db 57khz 4khz attenuation 2 att2 65 80 db 38khz attenuation 3 att3 35 50 db 67khz s / n ratio sn ? 35 ? ? ? db 57khz v in = 3mvrms ? demodulator ? not designed for radiation resistance. ? filter block ? ? 1.0 ? 0.3 ! ! ! ! output data timing t 1 t 5 t 1 =t 2 =4.3 s rclk rdata t 3 =t 4 =421 st 5 =t 6 =416.7 s t 1 t 3 t 4 t 2 t 6 t 2 the clock (rclk) frequency is 1187.5hz. depending on the state of the internal pll clock, the data (rdata) is replaced in synchronous with either the rising or falling or falling edge of the clock. to read the data, you may choose either the rising or falling edge of the clock as the reference. the data is valid for 416.7 s. after the reference clock edge. qual pin operation : indicates the quality of the demodulated data. (1) good data : hi (2) poor data : lo
bu1924 / bu1924f audio ics 5/5 ! ! ! ! electrical characteristic curves ? 70 ? 60 ? 50 ? 40 ? 30 ? 20 ? 10 0 10 20 30 filter gain : g ( db) fig.1 band-pass filter characteristics frequency : f ( khz) 10 20 30 40 50 60 70 80 90 100 ! ! ! ! external dimensions (units : mm) dip16 sop16 0.51min. 0.3 0.1 9 16 8 1 6.5 0.3 3.2 0.2 4.25 0.3 0.5 0.1 19.4 0.3 2.54 0 ~15 7.62 0.4 0.1 1.27 0.15 0.15 0.1 0.3min. 4.4 0.2 6.2 0.3 0.11 1.5 0.1 1 16 10.0 0.2 8 9 bu1924 bu1924f
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