BU1924

Audio ICs

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 andan 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 andcomponents, and FM pagers.

!Features1) 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)

ParameterPower supply voltageMaximum input voltageMaximum output voltagePower dissipationOperating temperatureStorage temperatureSymbolVDDVMax.IMax.PdToprTstgLimits−0.3~+7.0−0.3~VDD+0.3±4.0350∗−40~+85−55~+125UnitVVmAmW°C°CConditionsVDD1 VDD2All input pinsAll output pins−−−∗Reduced by 3.5mW for each increase in Ta of 1°C over 25°C.!Recommended operating conditions (Ta = 25°C)

ParameterPower supply voltageSymbolVDD1VDD2Min.4.54.5Typ.−−Max.5.55.5UnitVVBU1924 / BU1924F

Audio ICs

!Block diagram

560pCMPMUX270p(4)100kΩVSS3(7)(8)120kΩ100kΩ8th Switchedcapacitor filtercomparatorVref(3)anti-aliasing filter2.2µFVDD1(5)AnalogPower supply(16)RCLK∗1(1)QUALVSS1(6)∗1VDD2(12)DigitalPower supply(11)PLL57kHZRDS/ARIPLL1187.5HzBi-phasedecoderDifferentialdecoder(2)RDATA∗2VSS2Referenceclock(13)XI4.332MHZ(14)XO(10)Measurement circuit(9)T2T133pF33pF∗3∗3∗1 : VDD1 and VDD2 are separated within the IC.∗2 : Have VDD2 (digital power supply) of a sufficiently low impedance.∗3 : Match the capacitor constants with the crystal manufacturer.RCLK(N.C.)VDD2XOVSS2T1XI161514131211101QUAL2RDATA3Vref4MUX5VDD16VSS17VSS3CMPT298BU1924 / BU1924F

Audio ICs

!Pin descriptions

Pin No.12345678910111213141516SymbolQUALRDATAVrefMUXVDD1VSS1VSS3CMPT2T1VDD2VSS2XIXO(N.C.)RCLKPin nameFunctionsInput/Output typeType C−Type EType D−−C-junction (refer to input/output circuits )Open or connected to ground−Type DType B−Type A−Type CDemodulator qualityGood data : High, bad data : LowDemodulator dataReference voltageInputRefer to output data timing1/2 VDD1 (refer to input/output circuits)Composite signal input (refer to input/output circuits)Analog power supply4.5V to 5.5VGNDComparator inputTest inputDigital power supply4.5V to 5.5VConnects to 4.332MHz oscillator (refer to input/output circuits)−1187.5Hz clock (refer to the timing diagram)Crystal oscillator−Demodulator clock!Input / Output circuits

Type AType BType C10MΩType DType E++−BU1924 / BU1924F

Audio ICs

!Electrical characteristics (unless otherwise noted, Ta = 25°C, VDD1 = VDD2 = 5.0V, VSS1 = VSS2 = 0.0V)

ParameterOperating currentReference voltageInput current 1Output current 1Input current 2Output current 2Output high level voltage 1Output low level voltage 1〈Filter block〉Center frequencyGainAttenuation 1Attenuation 2Attenuation 3S / N ratioMaximum input level〈Demodulator〉RDS detector sensitivityRDS input levelARI detector sensitivityData rateClock transient vs. dataNot designed for radiation resistance.SymbolIDDVrefIIN1IOUT1IIN2IOUT2VOH1VOL1Min.−−−−−−VDD2−1.0−Typ.4.51/2VDD1−−−−VDD2−0.30.2Max.7.0−1.01.01.01.0−1.0UnitmAVµAµAµAµAVVIDD1+IDD2Pin 3MUXMUXXIXIConditionsVIN=VDD1VIN=VDD1VIN=VDD2VIN=VDD2RCLK RDATA QUAL IO=−1.0mARCLK RDATA QUAL IO=1.0mAFCGAATT1ATT2ATT3SNVMAX156.52018653530−−1.0−−−57.02322805040−0.5−1.51187.54.357.526−−−−500kHzdBdBdBdBdBmVrmsF=57.0kHz57kHz±4kHz38kHz67kHz57kHz VIN=3mVrmsSRDSMRDSSARIDRATECT1.03003.0−−mVrmsmVrmsmVrmsHzµs!Output data timing

RCLKRDATAT1T1=T2=4.3µST5T1T3T3=T4=421µST4T5=T6=416.7µST2T6T2The clock (RCLK) frequency is 1187.5Hz. Depending on the state of the internal PLL clock, the data (RDATA) is replacedin synchronous with either the rising or falling or falling edge of the clock. To read the data, you may choose either therising or falling edge of the clock as the reference. The data is valid for 416.7µs. 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

!Electrical characteristic curves

302010FILTER GAIN : G (dB)0−10−20−30−40−50−60−70102030405060708090100FREQUENCY : f (kHz)Fig.1 Band-pass filter characteristics!External dimensions (Units : mm)

BU1924BU1924F19.4±0.316910.0±0.26.5±0.31696.2±0.3187.620.51Min.4.4±0.23.2±0.24.25±0.310.3±0.12.540.5±0.10°~15°81.5±0.10.111.270.4±0.10.3Min.0.15DIP16SOP160.15±0.1