BA3880AS / BA3880AFS Audio ICs High-definition sound processor BA3880AS / BA3880AFS The BA3880AS and BA3880AFS are sound processor ICs that perform phase and harmonic compensation on audio signals to accurately reproduce the "rise" section of audio signals that determines the characteristics of the sound, and thus reproduce the original recording as naturally as possible. !Applications Component stereo systems, radio cassette players, car stereo systems, televisions, VCRs, and active speakers. !Features 1) Correct distortion in the rising section of audio signals that results from miss-matched speakers and amplifiers, and reproduces the original sound faithfully. 2) To allow application with all types of speakers and sources, the clarity can be adjusted using DC control. 3) DC control provided for selection of either processor mode or bypass mode. 4) Bass boost fixed internally to 4dB. !Block diagram BA3880AFS BA3880AS MIXL VCAL VCC 1 + + + + + HI MID + + + − 2 22 OUTL GND 24 1 DETL CTL 21 LO INL DETR 23 2 CTL 3 20 APFL DEFR 3 22 DEFR 21 VCC 20 VCAL 19 MIXL 18 OUTL 17 INL VCA HPF DEFL 4 19 CTL HPFL CTL 4 DETL 5 18 LPFL VCAR 5 GND 6 17 BIASC MIXR 6 DETR 7 16 LPFR OUTR 7 15 HPFR INR 8 DEFR − LO + + HI MID + + + + + + LPF CTL LPF 8 + + + + + HI MID LO + + + − HPF CTL 9 VCAR 10 MIXR 11 VCA VCA VCA − + + + HI + MID + + + + 14 APFR APFR 9 13 INR HPFR 10 HPF LO 16 15 APFL 14 HPFL 13 LPFL LPF 12 OUTR LPFR HPF 11 LPF BIASC 12 BA3880AS / BA3880AFS Audio ICs !Absolute maximum ratings (Ta = 25°C) Parameter Symbol Power supply voltage VCC Power dissipation Pd Limits Unit 11 V 1000 ∗ mW Operating temperature Topr −40~+85 °C Storage temperature Tstg −55~+125 °C ∗ Reduced by 10mW for each increase in Ta of 1°C over 25°C. !Recommended operating conditions Parameter Power supply voltage Symbol Limits Unit VCC 5.4~10.8 V !Electrical characteristics (unless otherwise noted, Ta = 25°C, VCC = 9V, fIN = 1kHz, VIN = 200mVrms, Rg = 600Ω, RL = 100k Ω and VCTL = 4.5V) Parameter Symbol Min. Typ. Max. Unit Conditions Circuit current ICC 3.9 5.9 11.8 mA VIN = 0Vrms Voltage gain 1 GV1 −2.0 0 2.0 dB VCTL = 9V Voltage gain 2 GV2 −2.5 −0.5 1.5 dB Voltage gain 3 GV3 −1.0 1.0 4.0 dB fIN = 10kHz Voltage gain 4 GV4 9.0 11.0 13.0 dB fIN = 10kHz, VCTL = 0V Voltage gain 5 GV5 − 4.0 − dB fIN = 50Hz Channel balance CB −2.0 0 2.0 dB fIN = 10kHz, VCTL = 0V Maximum output voltage VOM 2.0 2.3 − Vrms THD = 1% Output noise voltage 1 VNO1 − 2 10 µVrms Rg = 0Ω, DIN AUDIO, VCTL = 9V Output noise voltage 2 VNO2 − 16 70 µVrms Rg = 0Ω, DIN AUDIO Total harmonic distortion 1 THD1 − 0.005 0.05 % Total harmonic distortion 2 400Hz~30kHz BPF, VCTL = 9V THD2 − 0.04 0.4 % 400Hz~30kHz BPF Channel separation CS − −67 −60 dB VIN = 1Vrms Ripple rejection ratio RR 60 68 − dB Rg = 0Ω, fR = 100Hz, VR = 100mVrms ∗Note : When VCTL = 9V, the IC is in bypass mode (through operations). When VCTL = 4.5V, the IC is in processor mode (enhance operations) with minimum definition level. When VCTL = 0V, the IC is in processor mode (enhance operations) with maximum definition level. BA3880AS / BA3880AFS Audio ICs !Measurement circuit BA3880AS 4.7µ V 470p 1 MIXL OUTL 22 2 VCAL INL 21 3 VCC APFL 20 V THD 100k THD 100k 6800p A 4.7µ 600 0.01µ 0.1µ 47µ 9V 4 DEFL HPFL 19 5 DETL LPFL 18 6 GND BIASC 17 1µ 4.7µ 0.068µ BA3880AS 47µ 0.068µ 7 DETR LPFR 16 8 DEFR HPFR 15 4.7µ 1µ 4.7µ 0.01µ 9 CTL APFR 14 10 VCAR INR 13 11 MIXR OUTR 12 600 470p 9V 4.5V 4.7µ V 6800p Fig.1 V (Units) R : Ω C:F BA3880AS / BA3880AFS Audio ICs BA3880AFS 1 GND DETL 24 4.7µ 2 DETR 3 DEFR 23 4.7µ 1µ DEFL 22 1µ 0.1µ 4 CTL 5 VCAR VCC 21 VCAL 20 6800p 9V 47µ 9V A 6800p 4.5V 6 MIXR BA3880AFS MIXL 19 470p 4.7µ 470p V 7 OUTR 8 INR 9 APFR OUTL 18 INL 17 V 4.7µ V V THD 100k 4.7µ 16 0.01µ 600 10 HPFR APFL 15 11 LPFR HPFL 14 BIASC LPFL 13 600 0.01µ 0.068µ 12 47µ 0.068µ Fig.2 (Units) R : Ω C:F THD 100k BA3880AS / BA3880AFS Audio ICs !Circuit operation The BA3880AS and BA3880AFS high-definition sound processor system ICs treat the amplifiers and speakers as a total audio systems, and perform signal processing at the amplifier input stage to accurately reproduce the rise sections of audio signals that determine the characteristics of sound, and ensure that the replayed audio is as close to the original sound and as natural sounding as possible. Problems relating to playback of sound on audio systems. With naturally-generated sound, high-frequency harmonic components generally occur first, followed by the fundamental frequency components. This also applies to the attack section of the sound that characterizes many musical instruments. It is the amplitude component that gives form to the frequency component and envelope at the rising point of sound, and this expresses the characteristics of the sound. Therefore, when replaying audio on audio playback systems, it is extremely important that the rise section of the signal be expressed accurately with respect to the original sound. However, there is inevitable mismatching between the speakers and amplifiers in current audio systems. Solid-state power amplifiers use negative feedback techniques and operate off a fixed voltage supply, but as speakers are a current element, mismatching in the system inevitably occurs. In addition, the speaker impedance characteristics are strongly influenced by the electrical reactance of the voice coil, and the mechanical reactance of the cone assembly. As a result of this, distortion is generated in the rising sections of audio signals, causing phase shift in the reproduced sound. In addition, impedance increases in the treble region which reduces the speaker amplitude and reduces the harmonic component, and as a result there is a tendency to masking of large mid-frequency signal components that follow, and this makes it difficult to reproduce the rising sections of the sound. !Operating principle To solve the problems described above, the BA3880AS and BA3880AFS perform the audio signal processing described below. Phase shift compensation BASS 20 MIDDLE 150 TREBLE 2.4k 20k f (Hz) The input signal is separated into three regions: bass (20Hz to 150Hz), middle (150Hz to 2.4kHz) and treble (2.4kHz to 20kHz). These regions are then joined again with the middle and treble regions phase shifted −180° and −360° respectively with respect to the bass signal. This phase shift adjusts the delay time characteristic for each band and minimizes the distortion of the rising section of the audio signal. Amplitude compensation (harmonic compensation) To maintain appropriate auditory balance for the treble region that is made up of harmonic components, a high-speed detector and high-performance VCA circuit are used for amplitude control of the treble component. The amount of compensation is determined from a calculation performed based on the DC level input to the CTL pin, and the DC level detected from the input signal. The internal control signal obtained from this calculation compensates the amplitude of the treble component input to the VCA. This amplitude compensation recovers the harmonic component, and improves the reproduction clarity (definition level) of instruments and vocals. BA3880AS / BA3880AFS Audio ICs Bass boost To maintain good balance with the dynamically changing treble component, the bass component is boosted. The bass boost is fixed at 4dB (typ.) internally, and cannot be adjusted. Mode switch The DC voltage on the CTL pin can be used to switch the IC between processing mode and bypass mode. When processing mode is selected, the audio signal is enhanced using the compensation circuits described above before being output. When bypass mode is selected, the signal bypasses all of the compensation circuits, and only passes through a buffer amplifier before output. External components The frequency characteristic in processing mode with maximum definition level is given below. GAIN C1 LARGE C2 LARGE SMALL SMALL BASS BOOST DEFINITION LEVEL C1: External capacitor connected between the VCA and MIX pins (6800pF in the application circuit). C2: External capacitor connected between the OUT and MIX pins (470pF in the application circuit). FREQUENCY As indicated in the diagram, capacitors C1 and C2 determine the treble component cutoff frequency. By varying the values of these components, the frequency characteristic can be changed as indicated by the dotted line in the diagram. This varies the balance of the harmonic component, and is an important factor in determining the tone quality. Control table Item Threshold level Mode setting Definition level VCC Recommended setting range for bypass mode 0.75 × VCC 0.64 × VCC VCTL 0.57 × VCC Min. (1dB Typ.) 0.5 × VCC Recommended setting range for processor mode 0V (GND) Max. (11dB Typ.) BA3880AS / BA3880AFS Audio ICs !Application example BA3880AS 470p 1 68000p L−ch OUTPUT OUTL MIXL 22 + VCAL + + + 2 HI + 4.7µ + MID + + 21 LO 4.7µ − VCC VCC L−ch INPUT INL APFL 3 20 VCA 0.1µ 47µ DEFL HPF GND 4 HPFL 0.01µ 19 1µ CTL LPF DETL LPFL 5 18 4.7µ BIASC GND 6 0.068µ 17 LPFR DETR 7 47µ 0.068µ 16 4.7µ DEFR CTL LPF HPFR 8 15 1µ HPF APFR CTL VCTL 0.01µ VCA 9 + VCAR 10 68000p MIXR 14 − + + HI + + MID + + + R−ch INPUT INR LO 13 4.7µ R−ch OUTPUT OUTR 11 12 4.7µ 470p Fig.3 (Units) R : Ω C:F BA3880AS / BA3880AFS Audio ICs BA3880AFS DETL GND 24 1 4.7µ CTL DETR 23 2 4.7µ DEFR CTL DEFR 1µ GND 22 3 1µ CTL VCC VCA VCA VCTL 21 4 5 6800p MIXR 6 R−ch OUTPUT 470p VCC − LO + + + HI MID + + + + + VCAR VCAL 20 MIXL OUTL OUTR 7 18 INR INL 8 17 470p L−ch OUTPUT 4.7µ 4.7µ + + APFR 9 0.01µ 6800p 19 4.7µ R−ch INPUT 47µ 0.1µ HPFR HI HPF 4.7µ + + L−ch INPUT + 16 MID LO + + + − APFL 15 10 LPF HPFL LPFR HPF 11 0.068µ LPF BIASC 0.01µ 14 LPFL 13 12 47µ 0.068µ Fig.4 (Units) R : Ω C:F BA3880AS / BA3880AFS Audio ICs !Operation notes (1) Control pin (CTL) The level of the DC voltage applied to the control pin should be in the range 0V to VCC. Appropriate switching may not be possible in the region of the threshold voltage. Allow sufficient margin when setting this voltage. (2) Recommended operating range Provided the IC is operated within the operating temperature range and within the recommended operating conditions, the general circuit functions are guaranteed to operate correctly, and there will not be significant changes in the electrical characteristics. (3) Application example Provided the circuit constants in the application example circuit are used, the application circuit should function correctly. However, we recommend that you confirm the characteristics of the circuit in actual use, and take note of the cautionary items described above. If you change the circuit constants, check both the static and transient characteristics of the circuit, and allow sufficient margin to accommodate variations in both the IC and the external components. (4) License The ICs are manufactured under license from BBB Sound Inc. (U.S.A.). A license agreement with BBB Sound Inc. is required to use this component. !Electrical characteristic curves 16 VCC = 9V f = 10kHz VIN = 200mVrms 10 8 6 4 2 0 VCC = 9V f = 10kHz VCTL = 0V 14 DEFINITION LEVEL : (dB) DEFINITION LEVEL : (dB) 12 12 10 8 6 4 2 0 −10 −20 −30 −40 −50 −60 −70 −80 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 CONTROL VOLTAGE : VCTL (V) INPUT VOLTAGE : VIN (dBV) Fig. 3 Definition level vs. control voltage Fig. 4 Definition level vs. input voltage !External dimensions (Units : mm) BA3880AS BA3880AFS 10.0±0.2 19.4±0.3 0.5±0.1 0°~15° 13 1 12 0.8 0.36±0.1 0.15±0.1 7.8±0.3 1.8±0.1 0.3±0.1 1.778 0.11 7.62 11 1 24 5.4±0.2 12 6.5±0.3 0.51Min. 3.4±0.2 3.95±0.3 22 0.3Min. 0.15 SDIP22 SSOP-A24