BH3852FS

Audio ICs Sound control IC BH3852S / BH3852FS The BH3852S and BH3852FS are signal processing ICs designed for volume and tone control in CD radio cassettes and other audio products. They can be used without a microcomputer because they use DC current for control. FApplications CD radio cassettes, micro components, car stereos, televisions FFeatures 1) Can control volume (main volume) and tone (bass, treble). 2) Volume is produced by a low-distortion, low-noise VCA, is controlled with DC current, and, due to an internal reference voltage with temperature compensation, can control two channels with a single variable resistor. FAbsolute maximum ratings (Ta = 25_C) 3) Input amp can be used for gain adjustment, and matrix surround yields powerful sound. FRecommended operating conditions 611 Audio ICs FBlock diagram BH3852S / BH3852FS FPin descriptions 612 Audio ICs FInput / output circuits BH3852S / BH3852FS 613 Audio ICs BH3852S / BH3852FS 614 Audio ICs BH3852S / BH3852FS FElectrical characteristics(unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, BW = 20 X 20kHz, VOL = Max., TONE = ALL FLAT, Rg = 600Ω, RL = 10kΩ, INPUT_AMP_GAIN = 0dB) 615 Audio ICs FMeasurement circuit BH3852S / BH3852FS 616 Audio ICs FApplication example BH3852S / BH3852FS 617 Audio ICs FOperation notes (1) Operating power supply voltage range As long as the operating power supply voltage range and ambient temperature are kept within the specified range, the basic circuits are guaranteed to function, but be sure to check the constants as well as the element settings, voltage settings, and temperature settings. Also, volume curves sometimes depart from target values when there is a combination of low temperature and reduced power. (2) Primary amp BH3852S / BH3852FS S The input impedance is 47kΩ. S A buffer if R and C1 are not present. S The gain can be set by R and the 20kΩ. GVC = (R + 20kΩ) / R Note: Set C2 (input coupling) and C1 (used to set the gain) depending on the frequency band used. (3) Bass filter S The BPF is composed of a multifeedback active filter. fo can be varied according to the value of C. (theoretical equation) 1 2π R2 G= 5kΩ fO = 1 R1R2C1C2 C1 *1 1) C2 1 2 Q R1 R2C1C2 1 2 (C1)C2) *1 Note: Filter gain is calculated using the equation on the left. Total output gain is the sum of the gain for each of the internal circuits. (When R1 = 11.5kΩ, R2 = 85kΩ, C1 = C2 = C) fO = 5.1 10*6 C Q = 1.36 G = 8.5 618 Audio ICs (4) Treble filter BH3852S / BH3852FS S Cutoff frequency (fC1) for the bypass filter can be changed using the attached C3. fC1 = 1 2π C3 2kΩ The fC 1 for the recommended constant is approximately 8 kHz. S fC2 is determined by the band of the built-in amp. fC2 is approximately 100 kHz. Tone control is designed to yield a variation of ±15dB (Typ.) when the frequency to be boosted or cut is at the peak or bottom of the filter frequency characteristic, so please take the frequency characteristic into consideration in designing the filter. (5) Signal level setting The following figure represents the standard setting for the BH3852FS / BH3852S. LAs indicated above, if the front volume and rear volume input level are set so as not to exceed +6dBV (2Vrms), the pre-amp gain setting can be used to improve the S / N ratio. 619 Audio ICs BH3852S / BH3852FS (6) Matrix surround (7) DC control It is recommended that DC control of the VC, TC, BC, and SC pins be performed by voltage delivered in variable volume from the Vref pin (12th pin). When using variable volume, take the discharge current of each pin into account in determining its settings. Note:The voltage range for DC control is 0 (V) to Vref (V). Be sure not to apply voltage greater than Vref (V) to any pin. (8) GND If several capacitors with good high-frequency characteristics are connected in parallel to the 12th-pin capacitor, the characteristics will be improved with respect to static electricity noise. (Recommended : ceramic capacitors of 0.001µF to 0.1µF) The structure of the matrix surround is as shown in the figure above. Use the equations shown in the figure to calculate gain. 620 Audio ICs FElectrical characteristic curves BH3852S / BH3852FS FExternal dimensions (Units: mm) 621